Schedule bitmap animation timers on the compositor task runner.

third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h

Index: third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h
diff --git a/third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h b/third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h
index 8257671cd61b951964ed8dd95ffb99a6cd353d33..712b72d05a4388ed4d2718bfa49402c1799d9f8a 100644
--- a/third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h
+++ b/third_party/WebKit/Source/platform/scheduler/child/web_scheduler.h
@@ -72,6 +72,9 @@ class PLATFORM_EXPORT WebScheduler {
   // Returns a WebTaskRunner for timer tasks. Can be called from any thread.
   virtual WebTaskRunner* TimerTaskRunner() = 0;
 
+  // Returns a WebTaskRunner for compositor tasks.

[Sami, 2017/05/04 00:33:38]

Could add a bit more scary explanation here how this is only meant for specific
animation and rendering related tasks and should not be used generally?

[Dan Elphick, 2017/05/04 16:47:15]

Done.

+  virtual WebTaskRunner* CompositorTaskRunner() = 0;
+
   // Creates a new WebViewScheduler for a given WebView. Must be called from
   // the associated WebThread.
   virtual std::unique_ptr<WebViewScheduler> CreateWebViewScheduler(