Deliver IPC messages together with SwapCompositorFrame

cc/output/compositor_frame_metadata.h

Index: cc/output/compositor_frame_metadata.h
diff --git a/cc/output/compositor_frame_metadata.h b/cc/output/compositor_frame_metadata.h
index 54c3ce61a0fae5e8c0dab07b5c30d5e2a9ad31c1..6eda0a9866b2cdc46bac4192e95dfeaf13ee12b9 100644
--- a/cc/output/compositor_frame_metadata.h
+++ b/cc/output/compositor_frame_metadata.h
@@ -34,6 +34,9 @@ class CC_EXPORT CompositorFrameMetadata {
   float min_page_scale_factor;
   float max_page_scale_factor;
 
+  // Sequence number of the content that this frame was rendered for.
+  int source_frame_number;

[mkosiba (inactive), 2014/05/13 19:15:26]

this is only ever used by the SwapPromise. You think it would be better to pass
this in as an extra param to DidSwap?

+
   // Used to position the Android location top bar and page content, whose
   // precise position is computed by the renderer compositor.
   gfx::Vector2dF location_bar_offset;