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

content/browser/android/synchronous_compositor_host.cc

Index: content/browser/android/synchronous_compositor_host.cc
diff --git a/content/browser/android/synchronous_compositor_host.cc b/content/browser/android/synchronous_compositor_host.cc
index eb5a90fa6d0287d38f18ce369f439becf52ab5f9..cd1653efb1044b20281b7bc61d76af8d01af20e9 100644
--- a/content/browser/android/synchronous_compositor_host.cc
+++ b/content/browser/android/synchronous_compositor_host.cc
@@ -123,33 +123,32 @@ SynchronousCompositor::Frame SynchronousCompositorHost::DemandDrawHw(
   uint32_t compositor_frame_sink_id;
   cc::CompositorFrame compositor_frame;
   SyncCompositorCommonRendererParams common_renderer_params;
+  bool has_swapped;

[boliu, 2016/10/27 18:11:46]

initialize to false

 
   if (!sender_->Send(new SyncCompositorMsg_DemandDrawHw(
           routing_id_, params, &common_renderer_params,
-          &compositor_frame_sink_id, &compositor_frame))) {
+          &compositor_frame_sink_id, &compositor_frame, &has_swapped))) {
     return SynchronousCompositor::Frame();
   }
 
   ProcessCommonParams(common_renderer_params);
 
   return ProcessHardwareFrame(compositor_frame_sink_id,

[boliu, 2016/10/27 18:11:46]

just return empty frame if false, rather than passing it into another function

-                              std::move(compositor_frame));
+                              std::move(compositor_frame), has_swapped);
 }
 
 SynchronousCompositor::Frame SynchronousCompositorHost::ProcessHardwareFrame(
     uint32_t compositor_frame_sink_id,
-    cc::CompositorFrame compositor_frame) {
+    cc::CompositorFrame compositor_frame,
+    bool has_swapped) {
   SynchronousCompositor::Frame frame;
   frame.frame.reset(new cc::CompositorFrame);
   frame.compositor_frame_sink_id = compositor_frame_sink_id;
   *frame.frame = std::move(compositor_frame);
-  if (!frame.frame->delegated_frame_data) {
-    // This can happen if compositor did not swap in this draw.
-    frame.frame.reset();
-  }
-  if (frame.frame) {
+  if (has_swapped)
     UpdateFrameMetaData(frame.frame->metadata.Clone());
-  }
+  else
+    frame.frame.reset();
   return frame;
 }