Remove uses of external begin frame sources

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 2457b648018b8cbe9c0e67af364009ecc169c95b..3d35d23b9652eb690b2094132ae2a7e7ab6defee 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -217,8 +217,6 @@ class CONTENT_EXPORT RenderThreadImpl
   GetCompositorImplThreadTaskRunner() override;
   gpu::GpuMemoryBufferManager* GetGpuMemoryBufferManager() override;
   blink::scheduler::RendererScheduler* GetRendererScheduler() override;
-  std::unique_ptr<cc::BeginFrameSource> CreateExternalBeginFrameSource(
-      int routing_id) override;
   cc::ImageSerializationProcessor* GetImageSerializationProcessor() override;
   cc::TaskGraphRunner* GetTaskGraphRunner() override;
   bool AreImageDecodeTasksEnabled() override;
@@ -527,6 +525,9 @@ class CONTENT_EXPORT RenderThreadImpl
   void OnSyncMemoryPressure(
       base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
 
+  std::unique_ptr<cc::BeginFrameSource> CreateExternalBeginFrameSource(
+      int routing_id);
+
   // These objects live solely on the render thread.
   std::unique_ptr<AppCacheDispatcher> appcache_dispatcher_;
   std::unique_ptr<DomStorageDispatcher> dom_storage_dispatcher_;