Use observer pattern instead of sniffing SwapCompositorFrame IPC

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index 5caf7eab7947f091d5262799123294bcac397bac..e047cd495eaaafa35fcaedebb4d379da60947bd6 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -2631,6 +2631,8 @@ void RenderWidgetHostImpl::SubmitCompositorFrame(
     std::vector<ui::LatencyInfo>().swap(frame.metadata.latency_info);
   }
 
+  last_frame_metadata_ = frame.metadata.Clone();
+
   latency_tracker_.OnSwapCompositorFrame(&frame.metadata.latency_info);
 
   bool is_mobile_optimized = IsMobileOptimizedFrame(frame.metadata);
@@ -2659,6 +2661,9 @@ void RenderWidgetHostImpl::SubmitCompositorFrame(
       new_content_rendering_timeout_->IsRunning()) {
     new_content_rendering_timeout_->Stop();
   }
+
+  if (delegate_)
+    delegate_->DidReceiveCompositorFrame();
 }
 
 }  // namespace content