Remove uses of external begin frame sources

content/renderer/gpu/render_widget_compositor_delegate.h

Index: content/renderer/gpu/render_widget_compositor_delegate.h
diff --git a/content/renderer/gpu/render_widget_compositor_delegate.h b/content/renderer/gpu/render_widget_compositor_delegate.h
index f310041273a42e51acc37fcca6d69f0a8eb06e68..2d3171991095e67e19a7e9fd619628cf4315239f 100644
--- a/content/renderer/gpu/render_widget_compositor_delegate.h
+++ b/content/renderer/gpu/render_widget_compositor_delegate.h
@@ -38,10 +38,6 @@ class CONTENT_EXPORT RenderWidgetCompositorDelegate {
   virtual std::unique_ptr<cc::OutputSurface> CreateOutputSurface(
       bool fallback) = 0;
 
-  // Requests an external BeginFrameSource from the delegate.
-  virtual std::unique_ptr<cc::BeginFrameSource>
-  CreateExternalBeginFrameSource() = 0;
-
   // Notifies that the draw commands for a committed frame have been issued.
   virtual void DidCommitAndDrawCompositorFrame() = 0;