Implement PostDelayedTaskAt for guaranteed timer ordering

content/test/fake_renderer_scheduler.h

Index: content/test/fake_renderer_scheduler.h
diff --git a/content/test/fake_renderer_scheduler.h b/content/test/fake_renderer_scheduler.h
index b4082767adbc936d4dc25993bfa220241ee24a68..9f06e9e7a83c67139c59cbfc1a46911ea5e72b7e 100644
--- a/content/test/fake_renderer_scheduler.h
+++ b/content/test/fake_renderer_scheduler.h
@@ -15,12 +15,12 @@ class FakeRendererScheduler : public scheduler::RendererScheduler {
   ~FakeRendererScheduler() override;
 
   // RendererScheduler implementation.
-  scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() override;
+  scoped_refptr<scheduler::TaskQueue> DefaultTaskRunner() override;
   scoped_refptr<base::SingleThreadTaskRunner> CompositorTaskRunner() override;
   scoped_refptr<base::SingleThreadTaskRunner> LoadingTaskRunner() override;
   scoped_refptr<scheduler::SingleThreadIdleTaskRunner> IdleTaskRunner()
       override;
-  scoped_refptr<base::SingleThreadTaskRunner> TimerTaskRunner() override;
+  scoped_refptr<scheduler::TaskQueue> TimerTaskRunner() override;
   void WillBeginFrame(const cc::BeginFrameArgs& args) override;
   void BeginFrameNotExpectedSoon() override;
   void DidCommitFrameToCompositor() override;