Auto merge of #13058 - malisas:malisa-responseAPI, r=Manishearth,jdm

Response API

<!-- Please describe your changes on the following line: -->
This PR adds the [dom::Response](https://fetch.spec.whatwg.org/#response-class) implementation and addresses #11896.

The relevant passing tests` expectations have been updated.

In order to allow non-UTF-8-encoded status messages, `net_traits::response::Response`'s `raw_status` field has been changed from type [`Option<RawStatus>`](https://doc.servo.org/hyper/http/struct.RawStatus.html) to type `Option<(u16, Vec<u8>)>`. As a result, a few other files which rely on the `raw_status` field were affected and updated.

TODOs:
- The `body` and `trailer` methods. Relies on implementation of `ReadableStream` and `Promise`s.
- Similarly, replace the dummy constructor `_body: Option<USVString>` argument with `body: ResponseBodyInit`.
- Currently, whenever `r's response's header list` or `r's Headers object` are mentioned, I always modify the `headers_reflector` field (of type dom::Headers, or `r's Headers object`) and not the corresponding hyper::Headers list in the net_traits::Response field. A completely accurate interpretation of the spec might consider making both of these lists the same thing via a reference. [Discussion](https://github.com/whatwg/fetch/issues/358) was [had](https://github.com/servo/servo/pull/12884).

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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20 files changed, 385 insertions, 42 deletions

diff --git a/components/devtools/Cargo.toml b/components/devtools/Cargo.toml
index 230c16af6c2..f17488c575d 100644
--- a/components/devtools/Cargo.toml
+++ b/components/devtools/Cargo.toml
@@ -11,6 +11,7 @@ path = "lib.rs"
 
 [dependencies]
 devtools_traits = {path = "../devtools_traits"}
+encoding = "0.2"
 hyper = "0.9.9"
 hyper_serde = "0.1.4"
 ipc-channel = "0.5"
diff --git a/components/devtools/actors/network_event.rs b/components/devtools/actors/network_event.rs
index ba2793af8b7..9281356f7e5 100644
--- a/components/devtools/actors/network_event.rs
+++ b/components/devtools/actors/network_event.rs
@@ -11,12 +11,15 @@ extern crate hyper;
 use actor::{Actor, ActorMessageStatus, ActorRegistry};
 use devtools_traits::HttpRequest as DevtoolsHttpRequest;
 use devtools_traits::HttpResponse as DevtoolsHttpResponse;
+use encoding::all::UTF_8;
+use encoding::types::{DecoderTrap, Encoding};
 use hyper::header::Headers;
 use hyper::header::{ContentType, Cookie};
 use hyper::http::RawStatus;
 use hyper::method::Method;
 use protocol::JsonPacketStream;
 use serde_json::Value;
+use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::net::TcpStream;
 use time;
@@ -360,7 +363,10 @@ impl NetworkEventActor {
 
     pub fn add_response(&mut self, response: DevtoolsHttpResponse) {
         self.response.headers = response.headers.clone();
-        self.response.status = response.status.clone();
+        self.response.status = response.status.as_ref().map(|&(s, ref st)| {
+            let status_text = UTF_8.decode(st, DecoderTrap::Replace).unwrap();
+            RawStatus(s, Cow::from(status_text))
+        });
         self.response.body = response.body.clone();
      }
 
diff --git a/components/devtools/lib.rs b/components/devtools/lib.rs
index 17e36f95c0b..0ec2a713cde 100644
--- a/components/devtools/lib.rs
+++ b/components/devtools/lib.rs
@@ -21,6 +21,7 @@
 #![deny(unsafe_code)]
 
 extern crate devtools_traits;
+extern crate encoding;
 extern crate hyper;
 extern crate ipc_channel;
 #[macro_use]
diff --git a/components/devtools_traits/lib.rs b/components/devtools_traits/lib.rs
index ecaec49995b..4edf19d6f02 100644
--- a/components/devtools_traits/lib.rs
+++ b/components/devtools_traits/lib.rs
@@ -27,7 +27,6 @@ extern crate time;
 extern crate url;
 
 use hyper::header::Headers;
-use hyper::http::RawStatus;
 use hyper::method::Method;
 use ipc_channel::ipc::IpcSender;
 use msg::constellation_msg::PipelineId;
@@ -304,7 +303,7 @@ pub struct HttpRequest {
 #[derive(Debug, PartialEq)]
 pub struct HttpResponse {
     pub headers: Option<Headers>,
-    pub status: Option<RawStatus>,
+    pub status: Option<(u16, Vec<u8>)>,
     pub body: Option<Vec<u8>>,
     pub pipeline_id: PipelineId,
 }
diff --git a/components/net/about_loader.rs b/components/net/about_loader.rs
index 29f598f3cdf..26ec34d2e6c 100644
--- a/components/net/about_loader.rs
+++ b/components/net/about_loader.rs
@@ -4,7 +4,6 @@
 
 use file_loader;
 use hyper::header::ContentType;
-use hyper::http::RawStatus;
 use hyper::mime::{Mime, SubLevel, TopLevel};
 use hyper_serde::Serde;
 use mime_classifier::MimeClassifier;
@@ -38,7 +37,7 @@ pub fn factory(mut load_data: LoadData,
                     Some(Serde(ContentType(Mime(TopLevel::Text, SubLevel::Html, vec![])))),
                 charset: Some("utf-8".to_owned()),
                 headers: None,
-                status: Some(Serde(RawStatus(200, "OK".into()))),
+                status: Some((200, b"OK".to_vec())),
                 https_state: HttpsState::None,
                 referrer: None,
             };
diff --git a/components/net/blob_loader.rs b/components/net/blob_loader.rs
index 5cad922802a..1fe15d9a4a5 100644
--- a/components/net/blob_loader.rs
+++ b/components/net/blob_loader.rs
@@ -5,7 +5,6 @@
 use filemanager_thread::{FileManager, UIProvider};
 use hyper::header::{DispositionType, ContentDisposition, DispositionParam};
 use hyper::header::{Headers, ContentType, ContentLength, Charset};
-use hyper::http::RawStatus;
 use hyper_serde::Serde;
 use ipc_channel::ipc;
 use mime::{Mime, Attr};
@@ -72,7 +71,7 @@ fn load_blob<UI: 'static + UIProvider>
                     charset: charset.map(|c| c.as_str().to_string()),
                     headers: Some(Serde(headers)),
                     // https://w3c.github.io/FileAPI/#TwoHundredOK
-                    status: Some(Serde(RawStatus(200, "OK".into()))),
+                    status: Some((200, b"OK".to_vec())),
                     https_state: HttpsState::None,
                     referrer: None,
                 };
diff --git a/components/net/fetch/methods.rs b/components/net/fetch/methods.rs
index da2dda147fb..b9caa134712 100644
--- a/components/net/fetch/methods.rs
+++ b/components/net/fetch/methods.rs
@@ -973,8 +973,9 @@ fn http_network_fetch(request: Rc<Request>,
         Ok((res, msg)) => {
             response.url = Some(url.clone());
             response.status = Some(res.response.status);
-            response.raw_status = Some(res.response.status_raw().clone());
-            response.headers = res.response.headers.clone();
+            response.raw_status = Some((res.response.status_raw().0,
+                                        res.response.status_raw().1.as_bytes().to_vec()));
+                        response.headers = res.response.headers.clone();
 
             let res_body = response.body.clone();
 
@@ -1001,7 +1002,7 @@ fn http_network_fetch(request: Rc<Request>,
                                 send_response_to_devtools(
                                     &sender, request_id.unwrap(),
                                     meta_headers.map(Serde::into_inner),
-                                    meta_status.map(Serde::into_inner),
+                                    meta_status,
                                     pipeline_id);
                             }
                         }
diff --git a/components/net/http_loader.rs b/components/net/http_loader.rs
index 62df61bcd68..a2fd9f87f48 100644
--- a/components/net/http_loader.rs
+++ b/components/net/http_loader.rs
@@ -629,7 +629,7 @@ pub fn send_request_to_devtools(msg: ChromeToDevtoolsControlMsg,
 pub fn send_response_to_devtools(devtools_chan: &Sender<DevtoolsControlMsg>,
                              request_id: String,
                              headers: Option<Headers>,
-                             status: Option<RawStatus>,
+                             status: Option<(u16, Vec<u8>)>,
                              pipeline_id: PipelineId) {
     let response = DevtoolsHttpResponse { headers: headers, status: status, body: None, pipeline_id: pipeline_id };
     let net_event_response = NetworkEvent::HttpResponse(response);
@@ -1081,7 +1081,8 @@ pub fn load<A, B>(load_data: &LoadData,
             None => None
         });
         metadata.headers = Some(Serde(adjusted_headers));
-        metadata.status = Some(Serde(response.status_raw().clone()));
+        metadata.status = Some((response.status_raw().0,
+                                response.status_raw().1.as_bytes().to_vec()));
         metadata.https_state = if doc_url.scheme() == "https" {
             HttpsState::Modern
         } else {
@@ -1097,7 +1098,7 @@ pub fn load<A, B>(load_data: &LoadData,
                 send_response_to_devtools(
                     &chan, request_id.unwrap(),
                     metadata.headers.clone().map(Serde::into_inner),
-                    metadata.status.clone().map(Serde::into_inner),
+                    metadata.status.clone(),
                     pipeline_id);
             }
         }
diff --git a/components/net_traits/lib.rs b/components/net_traits/lib.rs
index a778d3ce76b..036fb54d940 100644
--- a/components/net_traits/lib.rs
+++ b/components/net_traits/lib.rs
@@ -560,9 +560,8 @@ pub struct Metadata {
     /// Headers
     pub headers: Option<Serde<Headers>>,
 
-    #[ignore_heap_size_of = "Defined in hyper"]
     /// HTTP Status
-    pub status: Option<Serde<RawStatus>>,
+    pub status: Option<(u16, Vec<u8>)>,
 
     /// Is successful HTTPS connection
     pub https_state: HttpsState,
@@ -580,7 +579,7 @@ impl Metadata {
             charset:      None,
             headers: None,
             // https://fetch.spec.whatwg.org/#concept-response-status-message
-            status: Some(Serde(RawStatus(200, "OK".into()))),
+            status: Some((200, b"OK".to_vec())),
             https_state: HttpsState::None,
             referrer: None,
         }
diff --git a/components/net_traits/response.rs b/components/net_traits/response.rs
index 37b0a585780..4305abd4fb6 100644
--- a/components/net_traits/response.rs
+++ b/components/net_traits/response.rs
@@ -5,7 +5,6 @@
 //! The [Response](https://fetch.spec.whatwg.org/#responses) object
 //! resulting from a [fetch operation](https://fetch.spec.whatwg.org/#concept-fetch)
 use hyper::header::{AccessControlExposeHeaders, ContentType, Headers};
-use hyper::http::RawStatus;
 use hyper::status::StatusCode;
 use hyper_serde::Serde;
 use std::ascii::AsciiExt;
@@ -15,7 +14,7 @@ use url::Url;
 use {Metadata, NetworkError};
 
 /// [Response type](https://fetch.spec.whatwg.org/#concept-response-type)
-#[derive(Clone, PartialEq, Copy, Debug, Deserialize, Serialize)]
+#[derive(Clone, PartialEq, Copy, Debug, Deserialize, Serialize, HeapSizeOf)]
 pub enum ResponseType {
     Basic,
     CORS,
@@ -26,7 +25,7 @@ pub enum ResponseType {
 }
 
 /// [Response termination reason](https://fetch.spec.whatwg.org/#concept-response-termination-reason)
-#[derive(Clone, Copy, Deserialize, Serialize)]
+#[derive(Clone, Copy, Deserialize, Serialize, HeapSizeOf)]
 pub enum TerminationReason {
     EndUserAbort,
     Fatal,
@@ -35,7 +34,7 @@ pub enum TerminationReason {
 
 /// The response body can still be pushed to after fetch
 /// This provides a way to store unfinished response bodies
-#[derive(Clone, Debug, PartialEq)]
+#[derive(Clone, Debug, PartialEq, HeapSizeOf)]
 pub enum ResponseBody {
     Empty, // XXXManishearth is this necessary, or is Done(vec![]) enough?
     Receiving(Vec<u8>),
@@ -53,7 +52,7 @@ impl ResponseBody {
 
 
 /// [Cache state](https://fetch.spec.whatwg.org/#concept-response-cache-state)
-#[derive(Clone, Debug, Deserialize, Serialize)]
+#[derive(Clone, Debug, Deserialize, Serialize, HeapSizeOf)]
 pub enum CacheState {
     None,
     Local,
@@ -76,16 +75,19 @@ pub enum ResponseMsg {
 }
 
 /// A [Response](https://fetch.spec.whatwg.org/#concept-response) as defined by the Fetch spec
-#[derive(Clone)]
+#[derive(Clone, HeapSizeOf)]
 pub struct Response {
     pub response_type: ResponseType,
     pub termination_reason: Option<TerminationReason>,
     pub url: Option<Url>,
     pub url_list: RefCell<Vec<Url>>,
     /// `None` can be considered a StatusCode of `0`.
+    #[ignore_heap_size_of = "Defined in hyper"]
     pub status: Option<StatusCode>,
-    pub raw_status: Option<RawStatus>,
+    pub raw_status: Option<(u16, Vec<u8>)>,
+    #[ignore_heap_size_of = "Defined in hyper"]
     pub headers: Headers,
+    #[ignore_heap_size_of = "Mutex heap size undefined"]
     pub body: Arc<Mutex<ResponseBody>>,
     pub cache_state: CacheState,
     pub https_state: HttpsState,
@@ -104,7 +106,7 @@ impl Response {
             url: None,
             url_list: RefCell::new(Vec::new()),
             status: Some(StatusCode::Ok),
-            raw_status: Some(RawStatus(200, "OK".into())),
+            raw_status: Some((200, b"OK".to_vec())),
             headers: Headers::new(),
             body: Arc::new(Mutex::new(ResponseBody::Empty)),
             cache_state: CacheState::None,
@@ -239,7 +241,7 @@ impl Response {
             None => None
         });
         metadata.headers = Some(Serde(self.headers.clone()));
-        metadata.status = self.raw_status.clone().map(Serde);
+        metadata.status = self.raw_status.clone();
         metadata.https_state = self.https_state;
         return Ok(metadata);
     }
diff --git a/components/script/dom/bindings/trace.rs b/components/script/dom/bindings/trace.rs
index 507e19e4bcb..49a27d3271a 100644
--- a/components/script/dom/bindings/trace.rs
+++ b/components/script/dom/bindings/trace.rs
@@ -50,6 +50,7 @@ use html5ever::tree_builder::QuirksMode;
 use hyper::header::Headers;
 use hyper::method::Method;
 use hyper::mime::Mime;
+use hyper::status::StatusCode;
 use ipc_channel::ipc::{IpcReceiver, IpcSender};
 use js::glue::{CallObjectTracer, CallUnbarrieredObjectTracer, CallValueTracer};
 use js::jsapi::{GCTraceKindToAscii, Heap, TraceKind, JSObject, JSTracer};
@@ -62,6 +63,7 @@ use net_traits::image::base::{Image, ImageMetadata};
 use net_traits::image_cache_thread::{ImageCacheChan, ImageCacheThread};
 use net_traits::request::Request;
 use net_traits::response::HttpsState;
+use net_traits::response::{Response, ResponseBody};
 use net_traits::storage_thread::StorageType;
 use net_traits::{Metadata, NetworkError, ResourceThreads};
 use offscreen_gl_context::GLLimits;
@@ -339,7 +341,10 @@ no_jsmanaged_fields!(SharedRt);
 no_jsmanaged_fields!(TouchpadPressurePhase);
 no_jsmanaged_fields!(USVString);
 no_jsmanaged_fields!(ReferrerPolicy);
+no_jsmanaged_fields!(Response);
+no_jsmanaged_fields!(ResponseBody);
 no_jsmanaged_fields!(ResourceThreads);
+no_jsmanaged_fields!(StatusCode);
 no_jsmanaged_fields!(SystemTime);
 no_jsmanaged_fields!(RelativePos);
 no_jsmanaged_fields!(OpaqueStyleAndLayoutData);
diff --git a/components/script/dom/headers.rs b/components/script/dom/headers.rs
index 7b45956c039..abfa959c8e6 100644
--- a/components/script/dom/headers.rs
+++ b/components/script/dom/headers.rs
@@ -209,7 +209,13 @@ impl Headers {
         headers_for_request
     }
 
-     pub fn set_guard(&self, new_guard: Guard) {
+    pub fn for_response(global: GlobalRef) -> Root<Headers> {
+        let headers_for_response = Headers::new(global);
+        headers_for_response.guard.set(Guard::Response);
+        headers_for_response
+    }
+
+    pub fn set_guard(&self, new_guard: Guard) {
         self.guard.set(new_guard)
     }
 
@@ -346,7 +352,7 @@ pub fn is_forbidden_header_name(name: &str) -> bool {
 // [3] https://tools.ietf.org/html/rfc7230#section-3.2.6
 // [4] https://www.rfc-editor.org/errata_search.php?rfc=7230
 fn validate_name_and_value(name: ByteString, value: ByteString)
-                           -> Result<(String, Vec<u8>), Error> {
+                           -> Fallible<(String, Vec<u8>)> {
     let valid_name = try!(validate_name(name));
     if !is_field_content(&value) {
         return Err(Error::Type("Value is not valid".to_string()));
@@ -354,7 +360,7 @@ fn validate_name_and_value(name: ByteString, value: ByteString)
     Ok((valid_name, value.into()))
 }
 
-fn validate_name(name: ByteString) -> Result<String, Error> {
+fn validate_name(name: ByteString) -> Fallible<String> {
     if !is_field_name(&name) {
         return Err(Error::Type("Name is not valid".to_string()));
     }
@@ -444,7 +450,7 @@ fn is_field_vchar(x: u8) -> bool {
 }
 
 // https://tools.ietf.org/html/rfc5234#appendix-B.1
-fn is_vchar(x: u8) -> bool {
+pub fn is_vchar(x: u8) -> bool {
     match x {
         0x21...0x7E => true,
         _ => false,
@@ -452,7 +458,7 @@ fn is_vchar(x: u8) -> bool {
 }
 
 // http://tools.ietf.org/html/rfc7230#section-3.2.6
-fn is_obs_text(x: u8) -> bool {
+pub fn is_obs_text(x: u8) -> bool {
     match x {
         0x80...0xFF => true,
         _ => false,
diff --git a/components/script/dom/htmllinkelement.rs b/components/script/dom/htmllinkelement.rs
index 9264bcb0490..07cd47cbcec 100644
--- a/components/script/dom/htmllinkelement.rs
+++ b/components/script/dom/htmllinkelement.rs
@@ -22,7 +22,6 @@ use dom::virtualmethods::VirtualMethods;
 use encoding::EncodingRef;
 use encoding::all::UTF_8;
 use hyper::header::ContentType;
-use hyper::http::RawStatus;
 use hyper::mime::{Mime, TopLevel, SubLevel};
 use hyper_serde::Serde;
 use ipc_channel::ipc;
@@ -335,7 +334,7 @@ impl AsyncResponseListener for StylesheetContext {
             document.invalidate_stylesheets();
 
             // FIXME: Revisit once consensus is reached at: https://github.com/whatwg/html/issues/1142
-            successful = metadata.status.map_or(false, |Serde(RawStatus(code, _))| code == 200);
+            successful = metadata.status.map_or(false, |(code, _)| code == 200);
         }
 
         if elem.parser_inserted.get() {
diff --git a/components/script/dom/htmlmediaelement.rs b/components/script/dom/htmlmediaelement.rs
index d26ac6a044e..c2db2b0b96f 100644
--- a/components/script/dom/htmlmediaelement.rs
+++ b/components/script/dom/htmlmediaelement.rs
@@ -24,7 +24,6 @@ use dom::htmlsourceelement::HTMLSourceElement;
 use dom::mediaerror::MediaError;
 use dom::node::{window_from_node, document_from_node, Node, UnbindContext};
 use dom::virtualmethods::VirtualMethods;
-use hyper_serde::Serde;
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
 use net_traits::{AsyncResponseListener, AsyncResponseTarget, Metadata, NetworkError};
@@ -66,7 +65,7 @@ impl AsyncResponseListener for HTMLMediaElementContext {
                              .as_ref()
                              .and_then(|m| m.status
                                             .as_ref()
-                                            .map(|&Serde(ref s)| s.0 < 200 || s.0 >= 300))
+                                            .map(|&(s, _)| s < 200 || s >= 300))
                              .unwrap_or(false);
         if is_failure {
             // Ensure that the element doesn't receive any further notifications
diff --git a/components/script/dom/htmlscriptelement.rs b/components/script/dom/htmlscriptelement.rs
index 6a6fe7d50b4..a7f5c5e3666 100644
--- a/components/script/dom/htmlscriptelement.rs
+++ b/components/script/dom/htmlscriptelement.rs
@@ -26,8 +26,6 @@ use dom::window::ScriptHelpers;
 use encoding::label::encoding_from_whatwg_label;
 use encoding::types::{DecoderTrap, EncodingRef};
 use html5ever::tree_builder::NextParserState;
-use hyper::http::RawStatus;
-use hyper_serde::Serde;
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
 use js::jsval::UndefinedValue;
@@ -159,7 +157,7 @@ impl AsyncResponseListener for ScriptContext {
 
         let status_code = self.metadata.as_ref().and_then(|m| {
             match m.status {
-                Some(Serde(RawStatus(c, _))) => Some(c),
+                Some((c, _)) => Some(c),
                 _ => None,
             }
         }).unwrap_or(0);
diff --git a/components/script/dom/mod.rs b/components/script/dom/mod.rs
index 07e4d6227be..f38d1e8949c 100644
--- a/components/script/dom/mod.rs
+++ b/components/script/dom/mod.rs
@@ -372,6 +372,7 @@ pub mod progressevent;
 pub mod radionodelist;
 pub mod range;
 pub mod request;
+pub mod response;
 pub mod screen;
 pub mod serviceworker;
 pub mod serviceworkercontainer;
diff --git a/components/script/dom/response.rs b/components/script/dom/response.rs
new file mode 100644
index 00000000000..acfc181283a
--- /dev/null
+++ b/components/script/dom/response.rs
@@ -0,0 +1,290 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use core::cell::Cell;
+use dom::bindings::cell::DOMRefCell;
+use dom::bindings::codegen::Bindings::HeadersBinding::HeadersMethods;
+use dom::bindings::codegen::Bindings::ResponseBinding;
+use dom::bindings::codegen::Bindings::ResponseBinding::{ResponseMethods, ResponseType as DOMResponseType};
+use dom::bindings::error::{Error, Fallible};
+use dom::bindings::global::GlobalRef;
+use dom::bindings::js::{JS, MutNullableHeap, Root};
+use dom::bindings::reflector::{Reflectable, Reflector, reflect_dom_object};
+use dom::bindings::str::{ByteString, USVString};
+use dom::headers::{Headers, Guard};
+use dom::headers::{is_vchar, is_obs_text};
+use hyper::status::StatusCode;
+use net_traits::response::{ResponseBody as NetTraitsResponseBody};
+use std::str::FromStr;
+use url::Position;
+use url::Url;
+
+#[dom_struct]
+pub struct Response {
+    reflector_: Reflector,
+    headers_reflector: MutNullableHeap<JS<Headers>>,
+    mime_type: DOMRefCell<Vec<u8>>,
+    body_used: Cell<bool>,
+    /// `None` can be considered a StatusCode of `0`.
+    #[ignore_heap_size_of = "Defined in hyper"]
+    status: DOMRefCell<Option<StatusCode>>,
+    raw_status: DOMRefCell<Option<(u16, Vec<u8>)>>,
+    response_type: DOMRefCell<DOMResponseType>,
+    url: DOMRefCell<Option<Url>>,
+    url_list: DOMRefCell<Vec<Url>>,
+    // For now use the existing NetTraitsResponseBody enum, until body
+    // is implemented.
+    body: DOMRefCell<NetTraitsResponseBody>,
+}
+
+impl Response {
+    pub fn new_inherited() -> Response {
+        Response {
+            reflector_: Reflector::new(),
+            headers_reflector: Default::default(),
+            mime_type: DOMRefCell::new("".to_string().into_bytes()),
+            body_used: Cell::new(false),
+            status: DOMRefCell::new(Some(StatusCode::Ok)),
+            raw_status: DOMRefCell::new(Some((200, b"OK".to_vec()))),
+            response_type: DOMRefCell::new(DOMResponseType::Default),
+            url: DOMRefCell::new(None),
+            url_list: DOMRefCell::new(vec![]),
+            body: DOMRefCell::new(NetTraitsResponseBody::Empty),
+        }
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response
+    pub fn new(global: GlobalRef) -> Root<Response> {
+        reflect_dom_object(box Response::new_inherited(), global, ResponseBinding::Wrap)
+    }
+
+    pub fn Constructor(global: GlobalRef, _body: Option<USVString>, init: &ResponseBinding::ResponseInit)
+                       -> Fallible<Root<Response>> {
+        // Step 1
+        if init.status < 200 || init.status > 599 {
+            return Err(Error::Range(
+                format!("init's status member should be in the range 200 to 599, inclusive, but is {}"
+                        , init.status)));
+        }
+
+        // Step 2
+        if !is_valid_status_text(&init.statusText) {
+            return Err(Error::Type("init's statusText member does not match the reason-phrase token production"
+                                   .to_string()));
+        }
+
+        // Step 3
+        let r = Response::new(global);
+
+        // Step 4
+        *r.status.borrow_mut() = Some(StatusCode::from_u16(init.status));
+
+        // Step 5
+        *r.raw_status.borrow_mut() = Some((init.status, init.statusText.clone().into()));
+
+        // Step 6
+        if let Some(ref headers_member) = init.headers {
+            // Step 6.1
+            // TODO: Figure out how/if we should make r's response's
+            // header list and r's Headers object the same thing. For
+            // now just working with r's Headers object. Also, the
+            // header list should already be empty so this step may be
+            // unnecessary.
+            r.Headers().empty_header_list();
+
+            // Step 6.2
+            try!(r.Headers().fill(Some(headers_member.clone())));
+        }
+
+        // Step 7
+        if let Some(_) = _body {
+            // Step 7.1
+            if is_null_body_status(init.status) {
+                return Err(Error::Type(
+                    "Body is non-null but init's status member is a null body status".to_string()));
+            };
+
+            // Step 7.2
+            let content_type: Option<ByteString> = None;
+
+            // Step 7.3
+            // TODO: Extract body and implement step 7.3.
+
+            // Step 7.4
+            if let Some(content_type_contents) = content_type {
+                if !r.Headers().Has(ByteString::new(b"Content-Type".to_vec())).unwrap() {
+                    try!(r.Headers().Append(ByteString::new(b"Content-Type".to_vec()), content_type_contents));
+                }
+            };
+        }
+
+        // Step 8
+        *r.mime_type.borrow_mut() = r.Headers().extract_mime_type();
+
+        // Step 9
+        // TODO: `entry settings object` is not implemented in Servo yet.
+
+        // Step 10
+        // TODO: Write this step once Promises are merged in
+
+        // Step 11
+        Ok(r)
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response-error
+    pub fn Error(global: GlobalRef) -> Root<Response> {
+        let r = Response::new(global);
+        *r.response_type.borrow_mut() = DOMResponseType::Error;
+        r.Headers().set_guard(Guard::Immutable);
+        *r.raw_status.borrow_mut() = Some((0, b"".to_vec()));
+        r
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response-redirect
+    pub fn Redirect(global: GlobalRef, url: USVString, status: u16) -> Fallible<Root<Response>> {
+        // Step 1
+        // TODO: `entry settings object` is not implemented in Servo yet.
+        let base_url = global.get_url();
+        let parsed_url = base_url.join(&url.0);
+
+        // Step 2
+        let url = match parsed_url {
+            Ok(url) => url,
+            Err(_) => return Err(Error::Type("Url could not be parsed".to_string())),
+        };
+
+        // Step 3
+        if !is_redirect_status(status) {
+            return Err(Error::Range("status is not a redirect status".to_string()));
+        }
+
+        // Step 4
+        // see Step 4 continued
+        let r = Response::new(global);
+
+        // Step 5
+        *r.status.borrow_mut() = Some(StatusCode::from_u16(status));
+        *r.raw_status.borrow_mut() = Some((status, b"".to_vec()));
+
+        // Step 6
+        let url_bytestring = ByteString::from_str(url.as_str()).unwrap_or(ByteString::new(b"".to_vec()));
+        try!(r.Headers().Set(ByteString::new(b"Location".to_vec()), url_bytestring));
+
+        // Step 4 continued
+        // Headers Guard is set to Immutable here to prevent error in Step 6
+        r.Headers().set_guard(Guard::Immutable);
+
+        // Step 7
+        Ok(r)
+    }
+}
+
+// https://fetch.spec.whatwg.org/#redirect-status
+fn is_redirect_status(status: u16) -> bool {
+    status == 301 || status == 302 || status == 303 || status == 307 || status == 308
+}
+
+// https://tools.ietf.org/html/rfc7230#section-3.1.2
+fn is_valid_status_text(status_text: &ByteString) -> bool {
+    // reason-phrase  = *( HTAB / SP / VCHAR / obs-text )
+    for byte in status_text.iter() {
+        if !(*byte == b'\t' || *byte == b' ' || is_vchar(*byte) || is_obs_text(*byte)) {
+            return false;
+        }
+    }
+    true
+}
+
+// https://fetch.spec.whatwg.org/#null-body-status
+fn is_null_body_status(status: u16) -> bool {
+    status == 101 || status == 204 || status == 205 || status == 304
+}
+
+impl ResponseMethods for Response {
+    // https://fetch.spec.whatwg.org/#dom-response-type
+    fn Type(&self) -> DOMResponseType {
+        *self.response_type.borrow()//into()
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response-url
+    fn Url(&self) -> USVString {
+        USVString(String::from((*self.url.borrow()).as_ref().map(|u| serialize_without_fragment(u)).unwrap_or("")))
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response-redirected
+    fn Redirected(&self) -> bool {
+        let url_list_len = self.url_list.borrow().len();
+        url_list_len > 1
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response-status
+    fn Status(&self) -> u16 {
+        match *self.raw_status.borrow() {
+            Some((s, _)) => s,
+            None => 0,
+        }
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response-ok
+    fn Ok(&self) -> bool {
+        match *self.status.borrow() {
+            Some(s) => {
+                let status_num = s.to_u16();
+                return status_num >= 200 && status_num <= 299;
+            }
+            None => false,
+        }
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response-statustext
+    fn StatusText(&self) -> ByteString {
+        match *self.raw_status.borrow() {
+            Some((_, ref st)) => ByteString::new(st.clone()),
+            None => ByteString::new(b"OK".to_vec()),
+        }
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response-headers
+    fn Headers(&self) -> Root<Headers> {
+        self.headers_reflector.or_init(|| Headers::for_response(self.global().r()))
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-response-clone
+    fn Clone(&self) -> Fallible<Root<Response>> {
+        // Step 1
+        // TODO: This step relies on body and stream, which are still unimplemented.
+
+        // Step 2
+        let new_response = Response::new(self.global().r());
+        new_response.Headers().set_guard(self.Headers().get_guard());
+
+        // https://fetch.spec.whatwg.org/#concept-response-clone
+        // Instead of storing a net_traits::Response internally, we
+        // only store the relevant fields, and only clone them here
+        *new_response.response_type.borrow_mut() = self.response_type.borrow().clone();
+        *new_response.status.borrow_mut() = self.status.borrow().clone();
+        *new_response.raw_status.borrow_mut() = self.raw_status.borrow().clone();
+        *new_response.url.borrow_mut() = self.url.borrow().clone();
+        *new_response.url_list.borrow_mut() = self.url_list.borrow().clone();
+
+        if *self.body.borrow() != NetTraitsResponseBody::Empty {
+            *new_response.body.borrow_mut() = self.body.borrow().clone();
+        }
+
+        // Step 3
+        // TODO: This step relies on promises, which are still unimplemented.
+
+        // Step 4
+        Ok(new_response)
+    }
+
+    // https://fetch.spec.whatwg.org/#dom-body-bodyused
+    fn BodyUsed(&self) -> bool {
+        self.body_used.get()
+    }
+}
+
+fn serialize_without_fragment(url: &Url) -> &str {
+    &url[..Position::AfterQuery]
+}
diff --git a/components/script/dom/webidls/Response.webidl b/components/script/dom/webidls/Response.webidl
new file mode 100644
index 00000000000..2052f5c6371
--- /dev/null
+++ b/components/script/dom/webidls/Response.webidl
@@ -0,0 +1,37 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://fetch.spec.whatwg.org/#response-class
+
+// TODO: pass 'optional ResponseBodyInit? body = null' to constructor in place of USVString
+ [Constructor(optional USVString? body = null, optional ResponseInit init),
+  Exposed=(Window,Worker)]
+interface Response {
+  [NewObject] static Response error();
+  [NewObject, Throws] static Response redirect(USVString url, optional unsigned short status = 302);
+
+  readonly attribute ResponseType type;
+
+  readonly attribute USVString url;
+  readonly attribute boolean redirected;
+  readonly attribute unsigned short status;
+  readonly attribute boolean ok;
+  readonly attribute ByteString statusText;
+  [SameObject] readonly attribute Headers headers;
+  // readonly attribute ReadableStream? body;
+  // [SameObject] readonly attribute Promise<Headers> trailer;
+
+  [NewObject, Throws] Response clone();
+};
+Response implements Body;
+
+dictionary ResponseInit {
+  unsigned short status = 200;
+  ByteString statusText = "OK";
+  HeadersInit headers;
+};
+
+enum ResponseType { "basic", "cors", "default", "error", "opaque", "opaqueredirect" };
+
+// typedef (BodyInit or ReadableStream) ResponseBodyInit;
diff --git a/components/script/dom/xmlhttprequest.rs b/components/script/dom/xmlhttprequest.rs
index 382e4c69faa..fc82d63a897 100644
--- a/components/script/dom/xmlhttprequest.rs
+++ b/components/script/dom/xmlhttprequest.rs
@@ -36,7 +36,6 @@ use encoding::types::{DecoderTrap, EncoderTrap, Encoding, EncodingRef};
 use euclid::length::Length;
 use hyper::header::Headers;
 use hyper::header::{ContentLength, ContentType};
-use hyper::http::RawStatus;
 use hyper::method::Method;
 use hyper::mime::{self, Mime, Attr as MimeAttr, Value as MimeValue};
 use hyper_serde::Serde;
@@ -91,7 +90,7 @@ struct XHRContext {
 #[derive(Clone)]
 pub enum XHRProgress {
     /// Notify that headers have been received
-    HeadersReceived(GenerationId, Option<Headers>, Option<RawStatus>),
+    HeadersReceived(GenerationId, Option<Headers>, Option<(u16, Vec<u8>)>),
     /// Partial progress (after receiving headers), containing portion of the response
     Loading(GenerationId, ByteString),
     /// Loading is done
@@ -879,7 +878,7 @@ impl XMLHttpRequest {
         self.process_partial_response(XHRProgress::HeadersReceived(
             gen_id,
             metadata.headers.map(Serde::into_inner),
-            metadata.status.map(Serde::into_inner)));
+            metadata.status));
         Ok(())
     }
 
@@ -943,9 +942,9 @@ impl XMLHttpRequest {
                 // Part of step 13, send() (processing response)
                 // XXXManishearth handle errors, if any (substep 1)
                 // Substep 2
-                status.map(|RawStatus(code, reason)| {
+                status.map(|(code, reason)| {
                     self.status.set(code);
-                    *self.status_text.borrow_mut() = ByteString::new(reason.into_owned().into_bytes());
+                    *self.status_text.borrow_mut() = ByteString::new(reason);
                 });
                 headers.as_ref().map(|h| *self.response_headers.borrow_mut() = h.clone());
 
diff --git a/components/servo/Cargo.lock b/components/servo/Cargo.lock
index f402fc54aa3..3d1c5a462e8 100644
--- a/components/servo/Cargo.lock
+++ b/components/servo/Cargo.lock
@@ -493,6 +493,7 @@ name = "devtools"
 version = "0.0.1"
 dependencies = [
  "devtools_traits 0.0.1",
+ "encoding 0.2.32 (registry+https://github.com/rust-lang/crates.io-index)",
  "hyper 0.9.10 (registry+https://github.com/rust-lang/crates.io-index)",
  "hyper_serde 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "ipc-channel 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",