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..e864be66a60c70fffc7a6e7099a9aaa696741366 100644
--- a/cc/output/compositor_frame_metadata.h
+++ b/cc/output/compositor_frame_metadata.h
@@ -41,6 +41,8 @@ class CC_EXPORT CompositorFrameMetadata {
   float overdraw_bottom_height;
 
   std::vector<ui::LatencyInfo> latency_info;
+  // Payload associated with this frame.
+  std::vector<IPC::Message> payload;

[mkosiba (inactive), 2014/05/06 22:30:33]

metadata seems to be the most convenient place for hacking but I imagine we want
this to liv in SwapCompositorFrame directly?

[piman, 2014/05/07 01:21:46]

I don't think we want to make cc depend on IPC.

I think we can relatively easily have it on the message, if the RWSwapPromise
has a way to get to the CompositorOutputSurface, since DidSwap is called before
the actual swap (the CompositorOutputSurface can stash whatever info from the
RWSwapPromise, and include it with the SwapCompositorFrame IPC)

[mkosiba (inactive), 2014/05/07 18:27:20]

true. The other reason I'm gravitating towards metadata is because the WebView
synchronous compositor doesn't use SwapCompositorFrame (and does use metadata)
but I could equally well add a bit of extra plumbing to the synchronous CC that
replicates whatever CompositorOutputSurface does).

 };
 
 }  // namespace cc