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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3 files changed, 5 insertions, 5 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;