Auto merge of #14008 - upsuper:rwlock, r=SimonSapin

Make style::context use parking_lot::RwLock

<!-- Please describe your changes on the following line: -->
The main motivation is to use `parking_lot::RwLock` instead of `sync::RwLock` in `style::context`, so that we can make `Stylesheet` be hold in a `parking_lot::RwLock` like other structs used for geckolib.

r? @SimonSapin

---
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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).

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- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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11 files changed, 23 insertions, 15 deletions

diff --git a/components/layout/Cargo.toml b/components/layout/Cargo.toml
index 6b7dabd9f15..917b6b82e73 100644
--- a/components/layout/Cargo.toml
+++ b/components/layout/Cargo.toml
@@ -27,6 +27,7 @@ log = "0.3.5"
 msg = {path = "../msg"}
 net_traits = {path = "../net_traits"}
 ordered-float = "0.2.2"
+parking_lot = {version = "0.3.3", features = ["nightly"]}
 plugins = {path = "../plugins"}
 profile_traits = {path = "../profile_traits"}
 range = {path = "../range"}
diff --git a/components/layout/context.rs b/components/layout/context.rs
index 17a484e2930..0b3973eac05 100644
--- a/components/layout/context.rs
+++ b/components/layout/context.rs
@@ -16,11 +16,12 @@ use ipc_channel::ipc;
 use net_traits::image::base::Image;
 use net_traits::image_cache_thread::{ImageCacheChan, ImageCacheThread, ImageResponse, ImageState};
 use net_traits::image_cache_thread::{ImageOrMetadataAvailable, UsePlaceholder};
+use parking_lot::RwLock;
 use std::cell::{RefCell, RefMut};
 use std::collections::HashMap;
 use std::hash::BuildHasherDefault;
 use std::rc::Rc;
-use std::sync::{Arc, Mutex, RwLock};
+use std::sync::{Arc, Mutex};
 use style::context::{LocalStyleContext, StyleContext, SharedStyleContext};
 use url::Url;
 use util::opts;
@@ -194,7 +195,6 @@ impl SharedLayoutContext {
                                        -> Option<WebRenderImageInfo> {
         if let Some(existing_webrender_image) = self.webrender_image_cache
                                                     .read()
-                                                    .unwrap()
                                                     .get(&((*url).clone(), use_placeholder)) {
             return Some((*existing_webrender_image).clone())
         }
@@ -205,9 +205,7 @@ impl SharedLayoutContext {
                 if image_info.key.is_none() {
                     Some(image_info)
                 } else {
-                    let mut webrender_image_cache = self.webrender_image_cache
-                                                        .write()
-                                                        .unwrap();
+                    let mut webrender_image_cache = self.webrender_image_cache.write();
                     webrender_image_cache.insert(((*url).clone(), use_placeholder),
                                                  image_info);
                     Some(image_info)
diff --git a/components/layout/lib.rs b/components/layout/lib.rs
index bff6eeca1ac..935a7631e23 100644
--- a/components/layout/lib.rs
+++ b/components/layout/lib.rs
@@ -36,6 +36,7 @@ extern crate log;
 extern crate msg;
 extern crate net_traits;
 extern crate ordered_float;
+extern crate parking_lot;
 #[macro_use]
 #[no_link]
 extern crate plugins as servo_plugins;
diff --git a/components/layout_thread/Cargo.toml b/components/layout_thread/Cargo.toml
index 37998d1b48b..368c6142980 100644
--- a/components/layout_thread/Cargo.toml
+++ b/components/layout_thread/Cargo.toml
@@ -25,6 +25,7 @@ lazy_static = "0.2"
 log = "0.3.5"
 msg = {path = "../msg"}
 net_traits = {path = "../net_traits"}
+parking_lot = {version = "0.3.3", features = ["nightly"]}
 plugins = {path = "../plugins"}
 profile_traits = {path = "../profile_traits"}
 script = {path = "../script"}
diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 8016bb68b44..32231f1808b 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -32,6 +32,7 @@ extern crate lazy_static;
 extern crate log;
 extern crate msg;
 extern crate net_traits;
+extern crate parking_lot;
 #[macro_use]
 extern crate profile_traits;
 extern crate script;
@@ -83,6 +84,7 @@ use layout_traits::LayoutThreadFactory;
 use msg::constellation_msg::PipelineId;
 use net_traits::image_cache_thread::{ImageCacheChan, ImageCacheResult, ImageCacheThread};
 use net_traits::image_cache_thread::UsePlaceholder;
+use parking_lot::RwLock;
 use profile_traits::mem::{self, Report, ReportKind, ReportsChan};
 use profile_traits::time::{self, TimerMetadata, profile};
 use profile_traits::time::{TimerMetadataFrameType, TimerMetadataReflowType};
@@ -101,7 +103,7 @@ use std::collections::HashMap;
 use std::hash::BuildHasherDefault;
 use std::ops::{Deref, DerefMut};
 use std::process;
-use std::sync::{Arc, Mutex, MutexGuard, RwLock};
+use std::sync::{Arc, Mutex, MutexGuard};
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::mpsc::{Receiver, Sender, channel};
 use style::animation::Animation;
@@ -1316,7 +1318,7 @@ impl LayoutThread {
 
         if let Some(mut root_flow) = self.root_flow.clone() {
             // Perform an abbreviated style recalc that operates without access to the DOM.
-            let animations = self.running_animations.read().unwrap();
+            let animations = self.running_animations.read();
             profile(time::ProfilerCategory::LayoutStyleRecalc,
                     self.profiler_metadata(),
                     self.time_profiler_chan.clone(),
@@ -1368,8 +1370,8 @@ impl LayoutThread {
             // Kick off animations if any were triggered, expire completed ones.
             animation::update_animation_state(&self.constellation_chan,
                                               &self.script_chan,
-                                              &mut *self.running_animations.write().unwrap(),
-                                              &mut *self.expired_animations.write().unwrap(),
+                                              &mut *self.running_animations.write(),
+                                              &mut *self.expired_animations.write(),
                                               &self.new_animations_receiver,
                                               self.id,
                                               &self.timer);
diff --git a/components/servo/Cargo.lock b/components/servo/Cargo.lock
index 0936aa8f0fc..7cdf39b2fc8 100644
--- a/components/servo/Cargo.lock
+++ b/components/servo/Cargo.lock
@@ -1149,6 +1149,7 @@ dependencies = [
  "msg 0.0.1",
  "net_traits 0.0.1",
  "ordered-float 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "plugins 0.0.1",
  "profile_traits 0.0.1",
  "range 0.0.1",
@@ -1194,6 +1195,7 @@ dependencies = [
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "msg 0.0.1",
  "net_traits 0.0.1",
+ "parking_lot 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "plugins 0.0.1",
  "profile_traits 0.0.1",
  "script 0.0.1",
diff --git a/components/style/animation.rs b/components/style/animation.rs
index 3cdc057d532..898dd8ee449 100644
--- a/components/style/animation.rs
+++ b/components/style/animation.rs
@@ -672,7 +672,7 @@ pub fn complete_expired_transitions(node: OpaqueNode, style: &mut Arc<ComputedVa
                                     context: &SharedStyleContext) -> bool {
     let had_animations_to_expire;
     {
-        let all_expired_animations = context.expired_animations.read().unwrap();
+        let all_expired_animations = context.expired_animations.read();
         let animations_to_expire = all_expired_animations.get(&node);
         had_animations_to_expire = animations_to_expire.is_some();
         if let Some(ref animations) = animations_to_expire {
@@ -686,7 +686,7 @@ pub fn complete_expired_transitions(node: OpaqueNode, style: &mut Arc<ComputedVa
     }
 
     if had_animations_to_expire {
-        context.expired_animations.write().unwrap().remove(&node);
+        context.expired_animations.write().remove(&node);
     }
 
     had_animations_to_expire
diff --git a/components/style/context.rs b/components/style/context.rs
index f25094140fa..fc3724452a7 100644
--- a/components/style/context.rs
+++ b/components/style/context.rs
@@ -10,10 +10,11 @@ use dom::OpaqueNode;
 use error_reporting::ParseErrorReporter;
 use euclid::Size2D;
 use matching::{ApplicableDeclarationsCache, StyleSharingCandidateCache};
+use parking_lot::RwLock;
 use selector_matching::Stylist;
 use std::cell::RefCell;
 use std::collections::HashMap;
-use std::sync::{Arc, Mutex, RwLock};
+use std::sync::{Arc, Mutex};
 use std::sync::mpsc::Sender;
 use timer::Timer;
 
diff --git a/components/style/gecko/data.rs b/components/style/gecko/data.rs
index e9d6dbf8627..1cc360fdeb8 100644
--- a/components/style/gecko/data.rs
+++ b/components/style/gecko/data.rs
@@ -12,11 +12,12 @@ use gecko_bindings::sugar::ownership::{HasBoxFFI, HasFFI, HasSimpleFFI};
 use media_queries::{Device, MediaType};
 use num_cpus;
 use parallel::WorkQueueData;
+use parking_lot::RwLock;
 use selector_matching::Stylist;
 use std::cmp;
 use std::collections::HashMap;
 use std::env;
-use std::sync::{Arc, RwLock};
+use std::sync::Arc;
 use std::sync::mpsc::{Receiver, Sender, channel};
 use style_traits::ViewportPx;
 use stylesheets::Stylesheet;
diff --git a/components/style/matching.rs b/components/style/matching.rs
index 3ede17edc38..6de269477a4 100644
--- a/components/style/matching.rs
+++ b/components/style/matching.rs
@@ -605,11 +605,10 @@ trait PrivateMatchMethods: TElement {
         // Merge any running transitions into the current style, and cancel them.
         let had_running_animations = context.running_animations
                                             .read()
-                                            .unwrap()
                                             .get(&this_opaque)
                                             .is_some();
         if had_running_animations {
-            let mut all_running_animations = context.running_animations.write().unwrap();
+            let mut all_running_animations = context.running_animations.write();
             for mut running_animation in all_running_animations.get_mut(&this_opaque).unwrap() {
                 // This shouldn't happen frequently, but under some
                 // circumstances mainly huge load or debug builds, the
diff --git a/ports/cef/Cargo.lock b/ports/cef/Cargo.lock
index 754b36a64d0..0513c40b90e 100644
--- a/ports/cef/Cargo.lock
+++ b/ports/cef/Cargo.lock
@@ -1056,6 +1056,7 @@ dependencies = [
  "msg 0.0.1",
  "net_traits 0.0.1",
  "ordered-float 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "plugins 0.0.1",
  "profile_traits 0.0.1",
  "range 0.0.1",
@@ -1094,6 +1095,7 @@ dependencies = [
  "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "msg 0.0.1",
  "net_traits 0.0.1",
+ "parking_lot 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "plugins 0.0.1",
  "profile_traits 0.0.1",
  "script 0.0.1",