sync compositor: Send ipc reply in swap

content/browser/android/in_process/synchronous_compositor_impl.cc

Index: content/browser/android/in_process/synchronous_compositor_impl.cc
diff --git a/content/browser/android/in_process/synchronous_compositor_impl.cc b/content/browser/android/in_process/synchronous_compositor_impl.cc
index 4d64521a57bde82141caef4440af9e771d808c81..e5c789b7b09686c7b16c3d1c6103aa883a803e65 100644
--- a/content/browser/android/in_process/synchronous_compositor_impl.cc
+++ b/content/browser/android/in_process/synchronous_compositor_impl.cc
@@ -4,6 +4,8 @@
 
 #include "content/browser/android/in_process/synchronous_compositor_impl.h"
 
+#include <utility>
+
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/lazy_instance.h"
@@ -163,19 +165,16 @@ scoped_ptr<cc::CompositorFrame> SynchronousCompositorImpl::DemandDrawHw(
   DCHECK(CalledOnValidThread());
   DCHECK(output_surface_);
   DCHECK(begin_frame_source_);
+  DCHECK(!frame_holder_);
 
-  scoped_ptr<cc::CompositorFrame> frame =
-      output_surface_->DemandDrawHw(surface_size,
-                                    transform,
-                                    viewport,
-                                    clip,
-                                    viewport_rect_for_tile_priority,
-                                    transform_for_tile_priority);
+  output_surface_->DemandDrawHw(surface_size, transform, viewport, clip,
+                                viewport_rect_for_tile_priority,
+                                transform_for_tile_priority);
 
-  if (frame.get())
-    UpdateFrameMetaData(frame->metadata);
+  if (frame_holder_)
+    UpdateFrameMetaData(frame_holder_->metadata);
 
-  return frame.Pass();
+  return std::move(frame_holder_);
 }
 
 void SynchronousCompositorImpl::ReturnResources(
@@ -188,14 +187,23 @@ bool SynchronousCompositorImpl::DemandDrawSw(SkCanvas* canvas) {
   DCHECK(CalledOnValidThread());
   DCHECK(output_surface_);
   DCHECK(begin_frame_source_);
+  DCHECK(!frame_holder_);
+
+  output_surface_->DemandDrawSw(canvas);
 
-  scoped_ptr<cc::CompositorFrame> frame =
-      output_surface_->DemandDrawSw(canvas);
+  bool success = !!frame_holder_;
+  if (frame_holder_) {
+    UpdateFrameMetaData(frame_holder_->metadata);
+    frame_holder_.reset();
+  }
 
-  if (frame.get())
-    UpdateFrameMetaData(frame->metadata);
+  return success;
+}
 
-  return !!frame.get();
+void SynchronousCompositorImpl::SwapBuffers(cc::CompositorFrame* frame) {
+  DCHECK(!frame_holder_);
+  frame_holder_.reset(new cc::CompositorFrame);
+  frame->AssignTo(frame_holder_.get());
 }
 
 void SynchronousCompositorImpl::UpdateFrameMetaData(