Add start_time to resource timing.

5 files changed, 272 insertions, 8 deletions

diff --git a/components/net/fetch/methods.rs b/components/net/fetch/methods.rs
index b60265ce2b8..d2250aa897a 100644
--- a/components/net/fetch/methods.rs
+++ b/components/net/fetch/methods.rs
@@ -21,8 +21,8 @@ use net_traits::filemanager_thread::RelativePos;
 use net_traits::request::{CredentialsMode, Destination, Referrer, Request, RequestMode};
 use net_traits::request::{Origin, ResponseTainting, Window};
 use net_traits::response::{Response, ResponseBody, ResponseType};
-use net_traits::ResourceAttribute;
 use net_traits::{FetchTaskTarget, NetworkError, ReferrerPolicy, ResourceFetchTiming};
+use net_traits::{ResourceAttribute, ResourceTimeValue};
 use servo_arc::Arc as ServoArc;
 use servo_url::ServoUrl;
 use std::borrow::Cow;
@@ -89,12 +89,19 @@ pub type DoneChannel = Option<(Sender<Data>, Receiver<Data>)>;
 
 /// [Fetch](https://fetch.spec.whatwg.org#concept-fetch)
 pub fn fetch(request: &mut Request, target: Target, context: &FetchContext) {
-    // Step 7 of https://w3c.github.io/resource-timing/#processing-model
+    // Steps 7,4 of https://w3c.github.io/resource-timing/#processing-model
+    // rev order okay since spec says they're equal - https://w3c.github.io/resource-timing/#dfn-starttime
     context
         .timing
         .lock()
         .unwrap()
         .set_attribute(ResourceAttribute::FetchStart);
+    context
+        .timing
+        .lock()
+        .unwrap()
+        .set_attribute(ResourceAttribute::StartTime(ResourceTimeValue::FetchStart));
+
     fetch_with_cors_cache(request, &mut CorsCache::new(), target, context);
 }
 
diff --git a/components/net/http_loader.rs b/components/net/http_loader.rs
index baf55b24faa..3bd8acce355 100644
--- a/components/net/http_loader.rs
+++ b/components/net/http_loader.rs
@@ -43,7 +43,9 @@ use net_traits::request::{RedirectMode, Referrer, Request, RequestBuilder, Reque
 use net_traits::request::{ResponseTainting, ServiceWorkersMode};
 use net_traits::response::{HttpsState, Response, ResponseBody, ResponseType};
 use net_traits::{CookieSource, FetchMetadata, NetworkError, ReferrerPolicy};
-use net_traits::{RedirectEndValue, RedirectStartValue, ResourceAttribute, ResourceFetchTiming};
+use net_traits::{
+    RedirectEndValue, RedirectStartValue, ResourceAttribute, ResourceFetchTiming, ResourceTimeValue,
+};
 use openssl::ssl::SslConnectorBuilder;
 use servo_arc::Arc;
 use servo_url::{ImmutableOrigin, ServoUrl};
@@ -572,8 +574,6 @@ pub fn http_fetch(
         // Generally, we use a persistent connection, so we will also set other PerformanceResourceTiming
         //   attributes to this as well (domain_lookup_start, domain_lookup_end, connect_start, connect_end,
         //   secure_connection_start)
-        // TODO(#21254) also set startTime equal to either fetch_start or redirect_start
-        //   (https://w3c.github.io/resource-timing/#dfn-starttime)
         context
             .timing
             .lock()
@@ -737,6 +737,21 @@ pub fn http_redirect_fetch(
         .unwrap()
         .set_attribute(ResourceAttribute::FetchStart);
 
+    // start_time should equal redirect_start if nonzero; else fetch_start
+    context
+        .timing
+        .lock()
+        .unwrap()
+        .set_attribute(ResourceAttribute::StartTime(ResourceTimeValue::FetchStart));
+
+    context
+        .timing
+        .lock()
+        .unwrap()
+        .set_attribute(ResourceAttribute::StartTime(
+            ResourceTimeValue::RedirectStart,
+        )); // updates start_time only if redirect_start is nonzero (implying TAO)
+
     // Step 5
     if request.redirect_count >= 20 {
         return Response::network_error(NetworkError::Internal("Too many redirects".into()));
diff --git a/components/net_traits/lib.rs b/components/net_traits/lib.rs
index ae6d8797adb..cdba4f2066d 100644
--- a/components/net_traits/lib.rs
+++ b/components/net_traits/lib.rs
@@ -474,6 +474,7 @@ pub struct ResourceFetchTiming {
     pub redirect_end: u64,
     pub connect_start: u64,
     pub connect_end: u64,
+    pub start_time: u64,
 }
 
 pub enum RedirectStartValue {
@@ -487,6 +488,15 @@ pub enum RedirectEndValue {
     ResponseEnd,
 }
 
+// TODO: refactor existing code to use this enum for setting time attributes
+// suggest using this with all time attributes in the future
+pub enum ResourceTimeValue {
+    Zero,
+    Now,
+    FetchStart,
+    RedirectStart,
+}
+
 pub enum ResourceAttribute {
     RedirectCount(u16),
     DomainLookupStart,
@@ -499,6 +509,7 @@ pub enum ResourceAttribute {
     ConnectEnd(u64),
     SecureConnectionStart,
     ResponseEnd,
+    StartTime(ResourceTimeValue),
 }
 
 #[derive(Clone, Copy, Debug, Deserialize, MallocSizeOf, PartialEq, Serialize)]
@@ -525,6 +536,7 @@ impl ResourceFetchTiming {
             connect_start: 0,
             connect_end: 0,
             response_end: 0,
+            start_time: 0,
         }
     }
 
@@ -532,7 +544,9 @@ impl ResourceFetchTiming {
     // time origin (as described in Performance::now)
     pub fn set_attribute(&mut self, attribute: ResourceAttribute) {
         let should_attribute_always_be_updated = match attribute {
-            ResourceAttribute::FetchStart | ResourceAttribute::ResponseEnd => true,
+            ResourceAttribute::FetchStart |
+            ResourceAttribute::ResponseEnd |
+            ResourceAttribute::StartTime(_) => true,
             _ => false,
         };
         if !self.timing_check_passed && !should_attribute_always_be_updated {
@@ -562,6 +576,20 @@ impl ResourceFetchTiming {
                 self.secure_connection_start = precise_time_ns()
             },
             ResourceAttribute::ResponseEnd => self.response_end = precise_time_ns(),
+            ResourceAttribute::StartTime(val) => match val {
+                ResourceTimeValue::RedirectStart
+                    if self.redirect_start == 0 || !self.timing_check_passed => {},
+                _ => self.start_time = self.get_time_value(val),
+            },
+        }
+    }
+
+    fn get_time_value(&self, time: ResourceTimeValue) -> u64 {
+        match time {
+            ResourceTimeValue::Zero => 0,
+            ResourceTimeValue::Now => precise_time_ns(),
+            ResourceTimeValue::FetchStart => self.fetch_start,
+            ResourceTimeValue::RedirectStart => self.redirect_start,
         }
     }
 
diff --git a/components/net_traits/tests/lib.rs b/components/net_traits/tests/lib.rs
new file mode 100644
index 00000000000..d54b77edb6a
--- /dev/null
+++ b/components/net_traits/tests/lib.rs
@@ -0,0 +1,215 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+use net_traits::{ResourceAttribute, ResourceFetchTiming, ResourceTimeValue, ResourceTimingType};
+
+#[test]
+fn test_set_start_time_to_fetch_start_if_nonzero_tao() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    resource_timing.fetch_start = 1;
+    assert_eq!(resource_timing.start_time, 0, "`start_time` should be zero");
+    assert!(
+        resource_timing.fetch_start > 0,
+        "`fetch_start` should have a positive value"
+    );
+
+    // verify that setting `start_time` to `fetch_start` succeeds
+    resource_timing.set_attribute(ResourceAttribute::StartTime(ResourceTimeValue::FetchStart));
+    assert_eq!(
+        resource_timing.start_time, resource_timing.fetch_start,
+        "`start_time` should equal `fetch_start`"
+    );
+}
+
+#[test]
+fn test_set_start_time_to_fetch_start_if_zero_tao() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    resource_timing.start_time = 1;
+    assert!(
+        resource_timing.start_time > 0,
+        "`start_time` should have a positive value"
+    );
+    assert_eq!(
+        resource_timing.fetch_start, 0,
+        "`fetch_start` should be zero"
+    );
+
+    // verify that setting `start_time` to `fetch_start` succeeds even when `fetch_start` == zero
+    resource_timing.set_attribute(ResourceAttribute::StartTime(ResourceTimeValue::FetchStart));
+    assert_eq!(
+        resource_timing.start_time, resource_timing.fetch_start,
+        "`start_time` should equal `fetch_start`"
+    );
+}
+
+#[test]
+fn test_set_start_time_to_fetch_start_if_nonzero_no_tao() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    resource_timing.mark_timing_check_failed();
+    resource_timing.fetch_start = 1;
+    assert_eq!(resource_timing.start_time, 0, "`start_time` should be zero");
+    assert!(
+        resource_timing.fetch_start > 0,
+        "`fetch_start` should have a positive value"
+    );
+
+    // verify that setting `start_time` to `fetch_start` succeeds even when TAO check failed
+    resource_timing.set_attribute(ResourceAttribute::StartTime(ResourceTimeValue::FetchStart));
+    assert_eq!(
+        resource_timing.start_time, resource_timing.fetch_start,
+        "`start_time` should equal `fetch_start`"
+    );
+}
+
+#[test]
+fn test_set_start_time_to_fetch_start_if_zero_no_tao() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    resource_timing.mark_timing_check_failed();
+    resource_timing.start_time = 1;
+    assert!(
+        resource_timing.start_time > 0,
+        "`start_time` should have a positive value"
+    );
+    assert_eq!(
+        resource_timing.fetch_start, 0,
+        "`fetch_start` should be zero"
+    );
+
+    // verify that setting `start_time` to `fetch_start` succeeds even when `fetch_start`==0 and no TAO
+    resource_timing.set_attribute(ResourceAttribute::StartTime(ResourceTimeValue::FetchStart));
+    assert_eq!(
+        resource_timing.start_time, resource_timing.fetch_start,
+        "`start_time` should equal `fetch_start`"
+    );
+}
+
+#[test]
+fn test_set_start_time_to_redirect_start_if_nonzero_tao() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    resource_timing.redirect_start = 1;
+    assert_eq!(resource_timing.start_time, 0, "`start_time` should be zero");
+    assert!(
+        resource_timing.redirect_start > 0,
+        "`redirect_start` should have a positive value"
+    );
+
+    // verify that setting `start_time` to `redirect_start` succeeds for nonzero `redirect_start`, TAO pass
+    resource_timing.set_attribute(ResourceAttribute::StartTime(
+        ResourceTimeValue::RedirectStart,
+    ));
+    assert_eq!(
+        resource_timing.start_time, resource_timing.redirect_start,
+        "`start_time` should equal `redirect_start`"
+    );
+}
+
+#[test]
+fn test_not_set_start_time_to_redirect_start_if_zero_tao() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    resource_timing.start_time = 1;
+    assert!(
+        resource_timing.start_time > 0,
+        "`start_time` should have a positive value"
+    );
+    assert_eq!(
+        resource_timing.redirect_start, 0,
+        "`redirect_start` should be zero"
+    );
+
+    // verify that setting `start_time` to `redirect_start` fails if `redirect_start` == 0
+    resource_timing.set_attribute(ResourceAttribute::StartTime(
+        ResourceTimeValue::RedirectStart,
+    ));
+    assert_ne!(
+        resource_timing.start_time, resource_timing.redirect_start,
+        "`start_time` should *not* equal `redirect_start`"
+    );
+}
+
+#[test]
+fn test_not_set_start_time_to_redirect_start_if_nonzero_no_tao() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    resource_timing.mark_timing_check_failed();
+    // Note: properly-behaved redirect_start should never be nonzero once TAO check has failed
+    resource_timing.redirect_start = 1;
+    assert_eq!(resource_timing.start_time, 0, "`start_time` should be zero");
+    assert!(
+        resource_timing.redirect_start > 0,
+        "`redirect_start` should have a positive value"
+    );
+
+    // verify that setting `start_time` to `redirect_start` fails if TAO check fails
+    resource_timing.set_attribute(ResourceAttribute::StartTime(
+        ResourceTimeValue::RedirectStart,
+    ));
+    assert_ne!(
+        resource_timing.start_time, resource_timing.redirect_start,
+        "`start_time` should *not* equal `redirect_start`"
+    );
+}
+
+#[test]
+fn test_not_set_start_time_to_redirect_start_if_zero_no_tao() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    resource_timing.mark_timing_check_failed();
+    resource_timing.start_time = 1;
+    assert!(
+        resource_timing.start_time > 0,
+        "`start_time` should have a positive value"
+    );
+    assert_eq!(
+        resource_timing.redirect_start, 0,
+        "`redirect_start` should be zero"
+    );
+
+    // verify that setting `start_time` to `redirect_start` fails if `redirect_start`==0 and no TAO
+    resource_timing.set_attribute(ResourceAttribute::StartTime(
+        ResourceTimeValue::RedirectStart,
+    ));
+    assert_ne!(
+        resource_timing.start_time, resource_timing.redirect_start,
+        "`start_time` should *not* equal `redirect_start`"
+    );
+}
+
+#[test]
+fn test_set_start_time() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    assert_eq!(
+        resource_timing.start_time, 0,
+        "initial `start_time` should be zero"
+    );
+
+    // verify setting `start_time` to current time succeeds
+    resource_timing.set_attribute(ResourceAttribute::StartTime(ResourceTimeValue::Now));
+    assert!(resource_timing.start_time > 0, "failed to set `start_time`");
+}
+#[test]
+fn test_reset_start_time() {
+    let mut resource_timing: ResourceFetchTiming =
+        ResourceFetchTiming::new(ResourceTimingType::Resource);
+    assert_eq!(resource_timing.start_time, 0, "initial `start_time` = 0");
+
+    resource_timing.start_time = 1;
+    assert!(
+        resource_timing.start_time > 0,
+        "`start_time` should have a positive value"
+    );
+
+    // verify resetting `start_time` (to zero) succeeds
+    resource_timing.set_attribute(ResourceAttribute::StartTime(ResourceTimeValue::Zero));
+    assert_eq!(
+        resource_timing.start_time, 0,
+        "failed to reset `start_time`"
+    );
+}
diff --git a/components/script/dom/performanceresourcetiming.rs b/components/script/dom/performanceresourcetiming.rs
index d3fc054d27b..735d13a31f4 100644
--- a/components/script/dom/performanceresourcetiming.rs
+++ b/components/script/dom/performanceresourcetiming.rs
@@ -55,7 +55,6 @@ pub struct PerformanceResourceTiming {
     decoded_body_size: u64, //size in octets
 }
 
-// TODO(#21254): startTime
 // TODO(#21255): duration
 // TODO(#21269): next_hop
 // TODO(#21264): worker_start
@@ -115,7 +114,7 @@ impl PerformanceResourceTiming {
             entry: PerformanceEntry::new_inherited(
                 DOMString::from(url.into_string()),
                 DOMString::from("resource"),
-                0.,
+                resource_timing.start_time as f64,
                 0.,
             ),
             initiator_type: initiator_type,