20 files changed, 38 insertions, 42 deletions
diff --git a/components/script/Cargo.toml b/components/script/Cargo.toml
index 3889402a346..8a200bc375f 100644
--- a/components/script/Cargo.toml
+++ b/components/script/Cargo.toml
@@ -19,6 +19,7 @@ unrooted_must_root_lint = ["script_plugins/unrooted_must_root_lint"]
 default = ["unrooted_must_root_lint"]
 webgl_backtrace = ["backtrace", "canvas_traits/webgl_backtrace"]
 js_backtrace = ["backtrace"]
+refcell_backtrace = ["accountable-refcell"]
 uwp = ["js/uwp"]
 vslatestinstalled = ["js/vslatestinstalled"]
 
@@ -31,6 +32,7 @@ serde_json = "1.0"
 tinyfiledialogs = "3.0"
 
 [dependencies]
+accountable-refcell = {version = "0.2.0", optional = true}
 app_units = "0.7"
 backtrace = {version = "0.3", optional = true}
 base64 = "0.10.1"
diff --git a/components/script/body.rs b/components/script/body.rs
index e38dd1b0a98..06b864fa4e9 100644
--- a/components/script/body.rs
+++ b/components/script/body.rs
@@ -3,6 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::compartments::{AlreadyInCompartment, InCompartment};
+use crate::dom::bindings::cell::Ref;
 use crate::dom::bindings::codegen::Bindings::FormDataBinding::FormDataMethods;
 use crate::dom::bindings::error::{Error, Fallible};
 use crate::dom::bindings::reflector::DomObject;
@@ -25,7 +26,6 @@ use js::rust::wrappers::JS_ParseJSON;
 use js::typedarray::{ArrayBuffer, CreateWith};
 use mime::{self, Mime};
 use script_traits::serializable::BlobImpl;
-use std::cell::Ref;
 use std::ptr;
 use std::rc::Rc;
 use std::str;
diff --git a/components/script/dom/attr.rs b/components/script/dom/attr.rs
index a25fcac3667..f81a3cf9817 100644
--- a/components/script/dom/attr.rs
+++ b/components/script/dom/attr.rs
@@ -2,7 +2,7 @@
  * 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 crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::AttrBinding::{self, AttrMethods};
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::root::{DomRoot, LayoutDom, MutNullableDom};
@@ -19,7 +19,6 @@ use dom_struct::dom_struct;
 use html5ever::{LocalName, Namespace, Prefix};
 use servo_atoms::Atom;
 use std::borrow::ToOwned;
-use std::cell::Ref;
 use std::mem;
 use style::attr::{AttrIdentifier, AttrValue};
 
diff --git a/components/script/dom/audiobuffer.rs b/components/script/dom/audiobuffer.rs
index f8a3f27093e..984445c8072 100644
--- a/components/script/dom/audiobuffer.rs
+++ b/components/script/dom/audiobuffer.rs
@@ -4,7 +4,7 @@
 
 use crate::compartments::enter_realm;
 use crate::dom::audionode::MAX_CHANNEL_COUNT;
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::AudioBufferBinding::{
     self, AudioBufferMethods, AudioBufferOptions,
 };
@@ -21,7 +21,6 @@ use js::rust::wrappers::DetachArrayBuffer;
 use js::rust::CustomAutoRooterGuard;
 use js::typedarray::{CreateWith, Float32Array};
 use servo_media::audio::buffer_source_node::AudioBuffer as ServoMediaAudioBuffer;
-use std::cell::Ref;
 use std::cmp::min;
 use std::ptr::{self, NonNull};
 
diff --git a/components/script/dom/bindings/cell.rs b/components/script/dom/bindings/cell.rs
index 525ac069fe3..e3f5ad71bee 100644
--- a/components/script/dom/bindings/cell.rs
+++ b/components/script/dom/bindings/cell.rs
@@ -4,7 +4,13 @@
 
 //! A shareable mutable container for the DOM.
 
-use std::cell::{BorrowError, BorrowMutError, Ref, RefCell, RefMut};
+#[cfg(feature = "refcell_backtrace")]
+pub use accountable_refcell::{ref_filter_map, Ref, RefCell, RefMut};
+#[cfg(not(feature = "refcell_backtrace"))]
+pub use ref_filter_map::ref_filter_map;
+use std::cell::{BorrowError, BorrowMutError};
+#[cfg(not(feature = "refcell_backtrace"))]
+pub use std::cell::{Ref, RefCell, RefMut};
 use style::thread_state::{self, ThreadState};
 
 /// A mutable field in the DOM.
diff --git a/components/script/dom/bluetooth.rs b/components/script/dom/bluetooth.rs
index fad367bb454..7ede2395c04 100644
--- a/components/script/dom/bluetooth.rs
+++ b/components/script/dom/bluetooth.rs
@@ -8,7 +8,7 @@ use bluetooth_traits::blocklist::{Blocklist, uuid_is_blocklisted};
 use bluetooth_traits::scanfilter::{BluetoothScanfilter, BluetoothScanfilterSequence};
 use bluetooth_traits::scanfilter::{RequestDeviceoptions, ServiceUUIDSequence};
 use crate::compartments::{AlreadyInCompartment, InCompartment};
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::BluetoothBinding::{self, BluetoothDataFilterInit};
 use crate::dom::bindings::codegen::Bindings::BluetoothBinding::{BluetoothMethods, RequestDeviceOptions};
 use crate::dom::bindings::codegen::Bindings::BluetoothBinding::BluetoothLEScanFilterInit;
@@ -39,7 +39,6 @@ use js::conversions::ConversionResult;
 use js::jsapi::JSObject;
 use js::jsval::{ObjectValue, UndefinedValue};
 use profile_traits::ipc as ProfiledIpc;
-use std::cell::Ref;
 use std::collections::HashMap;
 use std::rc::Rc;
 use std::str::FromStr;
diff --git a/components/script/dom/characterdata.rs b/components/script/dom/characterdata.rs
index 87aa8bd59fa..6baa6a855d9 100644
--- a/components/script/dom/characterdata.rs
+++ b/components/script/dom/characterdata.rs
@@ -4,7 +4,7 @@
 
 //! DOM bindings for `CharacterData`.
 
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::CharacterDataBinding::CharacterDataMethods;
 use crate::dom::bindings::codegen::Bindings::NodeBinding::NodeBinding::NodeMethods;
 use crate::dom::bindings::codegen::Bindings::ProcessingInstructionBinding::ProcessingInstructionMethods;
@@ -24,7 +24,6 @@ use crate::dom::processinginstruction::ProcessingInstruction;
 use crate::dom::text::Text;
 use crate::dom::virtualmethods::vtable_for;
 use dom_struct::dom_struct;
-use std::cell::Ref;
 
 // https://dom.spec.whatwg.org/#characterdata
 #[dom_struct]
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index c2058f73240..1f24a96c6a0 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -8,7 +8,7 @@ use crate::dom::activation::{synthetic_click_activation, ActivationSource};
 use crate::dom::attr::Attr;
 use crate::dom::beforeunloadevent::BeforeUnloadEvent;
 use crate::dom::bindings::callback::ExceptionHandling;
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{ref_filter_map, DomRefCell, Ref, RefMut};
 use crate::dom::bindings::codegen::Bindings::BeforeUnloadEventBinding::BeforeUnloadEventBinding::BeforeUnloadEventMethods;
 use crate::dom::bindings::codegen::Bindings::DocumentBinding;
 use crate::dom::bindings::codegen::Bindings::DocumentBinding::{
@@ -133,7 +133,6 @@ use num_traits::ToPrimitive;
 use percent_encoding::percent_decode;
 use profile_traits::ipc as profile_ipc;
 use profile_traits::time::{TimerMetadata, TimerMetadataFrameType, TimerMetadataReflowType};
-use ref_filter_map::ref_filter_map;
 use ref_slice::ref_slice;
 use script_layout_interface::message::{Msg, ReflowGoal};
 use script_traits::{AnimationState, DocumentActivity, MouseButton, MouseEventType};
@@ -146,7 +145,7 @@ use servo_config::pref;
 use servo_media::{ClientContextId, ServoMedia};
 use servo_url::{ImmutableOrigin, MutableOrigin, ServoUrl};
 use std::borrow::Cow;
-use std::cell::{Cell, Ref, RefMut};
+use std::cell::Cell;
 use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::collections::{HashMap, HashSet, VecDeque};
 use std::default::Default;
diff --git a/components/script/dom/dommatrixreadonly.rs b/components/script/dom/dommatrixreadonly.rs
index f8d73f628c1..acfd02bd56d 100644
--- a/components/script/dom/dommatrixreadonly.rs
+++ b/components/script/dom/dommatrixreadonly.rs
@@ -2,7 +2,7 @@
  * 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 crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::DOMMatrixBinding::{DOMMatrixInit, DOMMatrixMethods};
 use crate::dom::bindings::codegen::Bindings::DOMMatrixReadOnlyBinding::{
     DOMMatrixReadOnlyMethods, Wrap,
@@ -26,7 +26,7 @@ use js::jsapi::JSObject;
 use js::rust::CustomAutoRooterGuard;
 use js::typedarray::CreateWith;
 use js::typedarray::{Float32Array, Float64Array};
-use std::cell::{Cell, Ref};
+use std::cell::Cell;
 use std::f64;
 use std::ptr;
 use std::ptr::NonNull;
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index 7f956520ad2..00e70f2df02 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -6,7 +6,7 @@
 
 use crate::dom::activation::Activatable;
 use crate::dom::attr::{Attr, AttrHelpersForLayout};
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{ref_filter_map, DomRefCell, Ref, RefMut};
 use crate::dom::bindings::codegen::Bindings::AttrBinding::AttrMethods;
 use crate::dom::bindings::codegen::Bindings::DocumentBinding::DocumentMethods;
 use crate::dom::bindings::codegen::Bindings::ElementBinding;
@@ -98,7 +98,6 @@ use js::jsval::JSVal;
 use msg::constellation_msg::InputMethodType;
 use net_traits::request::CorsSettings;
 use net_traits::ReferrerPolicy;
-use ref_filter_map::ref_filter_map;
 use script_layout_interface::message::ReflowGoal;
 use selectors::attr::{AttrSelectorOperation, CaseSensitivity, NamespaceConstraint};
 use selectors::matching::{ElementSelectorFlags, MatchingContext};
@@ -107,7 +106,7 @@ use selectors::Element as SelectorsElement;
 use servo_arc::Arc;
 use servo_atoms::Atom;
 use std::borrow::Cow;
-use std::cell::{Cell, Ref, RefMut};
+use std::cell::Cell;
 use std::default::Default;
 use std::fmt;
 use std::mem;
diff --git a/components/script/dom/htmlcanvaselement.rs b/components/script/dom/htmlcanvaselement.rs
index 89410a6b6b0..e800a89bdf1 100644
--- a/components/script/dom/htmlcanvaselement.rs
+++ b/components/script/dom/htmlcanvaselement.rs
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::dom::attr::Attr;
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{ref_filter_map, DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::HTMLCanvasElementBinding;
 use crate::dom::bindings::codegen::Bindings::HTMLCanvasElementBinding::{
     HTMLCanvasElementMethods, RenderingContext,
@@ -44,7 +44,6 @@ use js::rust::HandleValue;
 use profile_traits::ipc;
 use script_layout_interface::{HTMLCanvasData, HTMLCanvasDataSource};
 use servo_config::pref;
-use std::cell::Ref;
 use style::attr::{AttrValue, LengthOrPercentageOrAuto};
 
 const DEFAULT_WIDTH: u32 = 300;
@@ -192,7 +191,7 @@ impl LayoutHTMLCanvasElementHelpers for LayoutDom<HTMLCanvasElement> {
 
 impl HTMLCanvasElement {
     pub fn context(&self) -> Option<Ref<CanvasContext>> {
-        ref_filter_map::ref_filter_map(self.context.borrow(), |ctx| ctx.as_ref())
+        ref_filter_map(self.context.borrow(), |ctx| ctx.as_ref())
     }
 
     fn get_or_init_2d_context(&self) -> Option<DomRoot<CanvasRenderingContext2D>> {
diff --git a/components/script/dom/htmlimageelement.rs b/components/script/dom/htmlimageelement.rs
index 5b6bd321534..fd2a58f8d7d 100644
--- a/components/script/dom/htmlimageelement.rs
+++ b/components/script/dom/htmlimageelement.rs
@@ -5,7 +5,7 @@
 use crate::document_loader::{LoadBlocker, LoadType};
 use crate::dom::activation::Activatable;
 use crate::dom::attr::Attr;
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, RefMut};
 use crate::dom::bindings::codegen::Bindings::DOMRectBinding::DOMRectBinding::DOMRectMethods;
 use crate::dom::bindings::codegen::Bindings::ElementBinding::ElementBinding::ElementMethods;
 use crate::dom::bindings::codegen::Bindings::HTMLImageElementBinding;
@@ -67,7 +67,7 @@ use num_traits::ToPrimitive;
 use servo_url::origin::ImmutableOrigin;
 use servo_url::origin::MutableOrigin;
 use servo_url::ServoUrl;
-use std::cell::{Cell, RefMut};
+use std::cell::Cell;
 use std::char;
 use std::collections::HashSet;
 use std::default::Default;
diff --git a/components/script/dom/mediastream.rs b/components/script/dom/mediastream.rs
index 2ae573b290e..88729b57ce5 100644
--- a/components/script/dom/mediastream.rs
+++ b/components/script/dom/mediastream.rs
@@ -2,7 +2,7 @@
  * 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 crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::MediaStreamBinding::{self, MediaStreamMethods};
 use crate::dom::bindings::error::Fallible;
 use crate::dom::bindings::reflector::{reflect_dom_object, DomObject};
@@ -14,7 +14,6 @@ use crate::dom::mediastreamtrack::MediaStreamTrack;
 use crate::dom::window::Window;
 use dom_struct::dom_struct;
 use servo_media::streams::MediaStreamType;
-use std::cell::Ref;
 
 #[dom_struct]
 pub struct MediaStream {
diff --git a/components/script/dom/node.rs b/components/script/dom/node.rs
index 6706b535092..0c5de3f67fb 100644
--- a/components/script/dom/node.rs
+++ b/components/script/dom/node.rs
@@ -6,7 +6,7 @@
 
 use crate::document_loader::DocumentLoader;
 use crate::dom::attr::Attr;
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref, RefMut};
 use crate::dom::bindings::codegen::Bindings::AttrBinding::AttrMethods;
 use crate::dom::bindings::codegen::Bindings::CharacterDataBinding::CharacterDataMethods;
 use crate::dom::bindings::codegen::Bindings::DocumentBinding::DocumentMethods;
@@ -86,7 +86,7 @@ use servo_arc::Arc;
 use servo_url::ServoUrl;
 use smallvec::SmallVec;
 use std::borrow::ToOwned;
-use std::cell::{Cell, Ref, RefMut, UnsafeCell};
+use std::cell::{Cell, UnsafeCell};
 use std::cmp;
 use std::default::Default;
 use std::iter;
diff --git a/components/script/dom/offscreencanvas.rs b/components/script/dom/offscreencanvas.rs
index 6d7cafed6f6..704918510a6 100644
--- a/components/script/dom/offscreencanvas.rs
+++ b/components/script/dom/offscreencanvas.rs
@@ -2,7 +2,7 @@
  * 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 crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{ref_filter_map, DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::OffscreenCanvasBinding::{
     OffscreenCanvasMethods, OffscreenRenderingContext, Wrap as OffscreenCanvasWrap,
 };
@@ -22,9 +22,7 @@ use euclid::default::Size2D;
 use ipc_channel::ipc::IpcSharedMemory;
 use js::rust::HandleValue;
 use profile_traits::ipc;
-use ref_filter_map;
 use std::cell::Cell;
-use std::cell::Ref;
 
 #[unrooted_must_root_lint::must_root]
 #[derive(Clone, JSTraceable, MallocSizeOf)]
@@ -94,7 +92,7 @@ impl OffscreenCanvas {
     }
 
     pub fn context(&self) -> Option<Ref<OffscreenCanvasContext>> {
-        ref_filter_map::ref_filter_map(self.context.borrow(), |ctx| ctx.as_ref())
+        ref_filter_map(self.context.borrow(), |ctx| ctx.as_ref())
     }
 
     pub fn fetch_all_data(&self) -> Option<(Option<IpcSharedMemory>, Size2D<u32>)> {
diff --git a/components/script/dom/request.rs b/components/script/dom/request.rs
index 29fd8a15c18..dcd206e3eaf 100644
--- a/components/script/dom/request.rs
+++ b/components/script/dom/request.rs
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::body::{consume_body, BodyOperations, BodyType};
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::HeadersBinding::{HeadersInit, HeadersMethods};
 use crate::dom::bindings::codegen::Bindings::RequestBinding;
 use crate::dom::bindings::codegen::Bindings::RequestBinding::ReferrerPolicy;
@@ -38,7 +38,7 @@ use net_traits::request::RequestMode as NetTraitsRequestMode;
 use net_traits::request::{Origin, Window};
 use net_traits::ReferrerPolicy as MsgReferrerPolicy;
 use servo_url::ServoUrl;
-use std::cell::{Cell, Ref};
+use std::cell::Cell;
 use std::rc::Rc;
 use std::str::FromStr;
 
diff --git a/components/script/dom/response.rs b/components/script/dom/response.rs
index 0e756513b9a..802e803b17f 100644
--- a/components/script/dom/response.rs
+++ b/components/script/dom/response.rs
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::body::{consume_body, consume_body_with_promise, BodyOperations, BodyType};
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::HeadersBinding::{HeadersInit, HeadersMethods};
 use crate::dom::bindings::codegen::Bindings::ResponseBinding;
 use crate::dom::bindings::codegen::Bindings::ResponseBinding::{
@@ -26,7 +26,7 @@ use hyper::StatusCode;
 use hyper_serde::Serde;
 use net_traits::response::ResponseBody as NetTraitsResponseBody;
 use servo_url::ServoUrl;
-use std::cell::{Cell, Ref};
+use std::cell::Cell;
 use std::mem;
 use std::rc::Rc;
 use std::str::FromStr;
diff --git a/components/script/dom/webglprogram.rs b/components/script/dom/webglprogram.rs
index e4f5f89c6d3..3b040a170b1 100644
--- a/components/script/dom/webglprogram.rs
+++ b/components/script/dom/webglprogram.rs
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://www.khronos.org/registry/webgl/specs/latest/1.0/webgl.idl
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::WebGLProgramBinding;
 use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLRenderingContextConstants as constants;
 use crate::dom::bindings::inheritance::Castable;
@@ -19,7 +19,7 @@ use canvas_traits::webgl::{webgl_channel, WebGLProgramId, WebGLResult};
 use canvas_traits::webgl::{ActiveAttribInfo, ActiveUniformInfo, WebGLCommand, WebGLError};
 use dom_struct::dom_struct;
 use fnv::FnvHashSet;
-use std::cell::{Cell, Ref};
+use std::cell::Cell;
 
 #[dom_struct]
 pub struct WebGLProgram {
diff --git a/components/script/dom/webglvertexarrayobjectoes.rs b/components/script/dom/webglvertexarrayobjectoes.rs
index e54eaf3f04a..1d802968ae1 100644
--- a/components/script/dom/webglvertexarrayobjectoes.rs
+++ b/components/script/dom/webglvertexarrayobjectoes.rs
@@ -2,7 +2,7 @@
  * 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 crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{ref_filter_map, DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLRenderingContextConstants as constants;
 use crate::dom::bindings::codegen::Bindings::WebGLVertexArrayObjectOESBinding;
 use crate::dom::bindings::inheritance::Castable;
@@ -15,8 +15,7 @@ use canvas_traits::webgl::{
     ActiveAttribInfo, WebGLCommand, WebGLError, WebGLResult, WebGLVertexArrayId,
 };
 use dom_struct::dom_struct;
-use ref_filter_map::ref_filter_map;
-use std::cell::{Cell, Ref};
+use std::cell::Cell;
 
 #[dom_struct]
 pub struct WebGLVertexArrayObjectOES {
diff --git a/components/script/dom/workerglobalscope.rs b/components/script/dom/workerglobalscope.rs
index 8624208423e..f29fd70f99f 100644
--- a/components/script/dom/workerglobalscope.rs
+++ b/components/script/dom/workerglobalscope.rs
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::compartments::InCompartment;
-use crate::dom::bindings::cell::DomRefCell;
+use crate::dom::bindings::cell::{DomRefCell, Ref};
 use crate::dom::bindings::codegen::Bindings::RequestBinding::RequestInit;
 use crate::dom::bindings::codegen::Bindings::WorkerBinding::WorkerType;
 use crate::dom::bindings::codegen::Bindings::WorkerGlobalScopeBinding::WorkerGlobalScopeMethods;
@@ -52,7 +52,6 @@ use net_traits::request::{
 use net_traits::IpcSend;
 use script_traits::WorkerGlobalScopeInit;
 use servo_url::{MutableOrigin, ServoUrl};
-use std::cell::Ref;
 use std::default::Default;
 use std::rc::Rc;
 use std::sync::atomic::{AtomicBool, Ordering};