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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1 files changed, 6 insertions, 4 deletions

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);