Splitting DidSwap in cc::SwapPromise into WillSwap and DidSwap

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index de50e70ea351370c82a80dde3788be6b893962c6..29711d1d26a3e9c99ccde552c0a7095662206c1e 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1666,6 +1666,8 @@ bool LayerTreeHostImpl::DrawLayers(FrameData* frame) {
   compositor_frame.render_pass_list = std::move(frame->render_passes);
   compositor_frame_sink_->SubmitCompositorFrame(std::move(compositor_frame));
 
+  active_tree()->ClearSwapPromises();

[vmpstr, 2016/12/15 21:54:31]

Add a comment here please

[Saman Sami, 2016/12/15 22:11:58]

Done.

+
   // The next frame should start by assuming nothing has changed, and changes
   // are noted as they occur.
   // TODO(boliu): If we did a temporary software renderer frame, propogate the