Remove uses of external begin frame sources

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index 430c7c9b7acaf27a0893850fec98a5d40ce049e6..eb730cd651d5bcd0d8202dce7d3bc63ff35030d2 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -748,11 +748,6 @@ std::unique_ptr<cc::OutputSurface> RenderWidget::CreateOutputSurface(
       GetURLForGraphicsContext3D());
 }
 
-std::unique_ptr<cc::BeginFrameSource>
-RenderWidget::CreateExternalBeginFrameSource() {
-  return compositor_deps_->CreateExternalBeginFrameSource(routing_id_);
-}
-
 void RenderWidget::DidCommitAndDrawCompositorFrame() {
   // NOTE: Tests may break if this event is renamed or moved. See
   // tab_capture_performancetest.cc.