Added MojoCompositorFrameSink::EvictFrame() and MojoCompositorFrameSinkClient::WillDrawSurface()

cc/ipc/mojo_compositor_frame_sink.mojom

Index: cc/ipc/mojo_compositor_frame_sink.mojom
diff --git a/cc/ipc/mojo_compositor_frame_sink.mojom b/cc/ipc/mojo_compositor_frame_sink.mojom
index cedd96615e4edc5190470ac314d472cb60c4fd94..5c6d77e38e494c907a98115ce8aa65301b3db908 100644
--- a/cc/ipc/mojo_compositor_frame_sink.mojom
+++ b/cc/ipc/mojo_compositor_frame_sink.mojom
@@ -31,6 +31,10 @@ interface MojoCompositorFrameSink {
   SubmitCompositorFrame(cc.mojom.LocalFrameId local_frame_id,
                         cc.mojom.CompositorFrame frame);
 
+  // Notify that the surface is no longer in use (and is okay to be evicted) so
+  // that its resources gets returned in time.
+  EvictFrame();
+
   // TODO(fsamuel): ReadbackBitmap API would be useful here.
 };
 
@@ -49,6 +53,9 @@ interface MojoCompositorFrameSinkClient {
 
   // Returns resources sent to SubmitCompositorFrame to be reused or freed.
   ReclaimResources(ReturnedResourceArray resources);
+
+  // Called when surface is being scheduled for a draw.
+  WillDrawSurface();

[danakj, 2016/12/02 00:01:14]

no damage rect or local frame id?

[Alex Z., 2016/12/02 16:17:15]

This was first added in https://codereview.chromium.org/2493223002/ for
exo::Surface.
Local frame ID was not needed because exo::Surface manages its own damage rect
and local frame ID. 
exo::Surface doesn't need a damage rect for its own WillDraw().

MojoCompositorFrameSink::SubmitCompositorFrame() now takes a LocalFrameId so I
think it should be fine.

 };
 
 // MojoCompositorFrameSinkPrivate is used by the display compositor host to set