Switching to base::Optional<CompositorFrame> in Android's synchronous compositor IPC messages

content/renderer/android/synchronous_compositor_proxy.cc

Index: content/renderer/android/synchronous_compositor_proxy.cc
diff --git a/content/renderer/android/synchronous_compositor_proxy.cc b/content/renderer/android/synchronous_compositor_proxy.cc
index fde29a64d26f869494af4d179e51faac6fe63d26..761ce27b86e60e46fd32769fad55b0024500fd28 100644
--- a/content/renderer/android/synchronous_compositor_proxy.cc
+++ b/content/renderer/android/synchronous_compositor_proxy.cc
@@ -188,9 +188,10 @@ void SynchronousCompositorProxy::DoDemandDrawHw(
   if (inside_receive_) {
     // Did not swap.
     if (!reply_message) {
-      SendDemandDrawHwReplyAsync(cc::CompositorFrame(), 0u);
+      SendDemandDrawHwReplyAsync(base::Optional<cc::CompositorFrame>(), 0u);

[boliu, 2016/10/27 19:52:16]

would nullptr work here?

     } else {
-      SendDemandDrawHwReply(cc::CompositorFrame(), 0u, reply_message);
+      SendDemandDrawHwReply(base::Optional<cc::CompositorFrame>(), 0u,
+                            reply_message);
     }
     inside_receive_ = false;
   }
@@ -216,14 +217,14 @@ void SynchronousCompositorProxy::SubmitCompositorFrameHw(
 }
 
 void SynchronousCompositorProxy::SendDemandDrawHwReplyAsync(
-    cc::CompositorFrame frame,
+    base::Optional<cc::CompositorFrame> frame,
     uint32_t compositor_frame_sink_id) {
   Send(new SyncCompositorHostMsg_ReturnFrame(routing_id_,
                                              compositor_frame_sink_id, frame));
 }
 
 void SynchronousCompositorProxy::SendDemandDrawHwReply(
-    cc::CompositorFrame frame,
+    base::Optional<cc::CompositorFrame> frame,
     uint32_t compositor_frame_sink_id,
     IPC::Message* reply_message) {
   SyncCompositorCommonRendererParams common_renderer_params;