sync compositor: Signal async frame on IO thread

content/public/browser/android/synchronous_compositor.h

Index: content/public/browser/android/synchronous_compositor.h
diff --git a/content/public/browser/android/synchronous_compositor.h b/content/public/browser/android/synchronous_compositor.h
index a4d5b40e91edb64c96fc6df5772c0a8f946d5b65..660997ca9020d9e703188b6a1ec0b13f4dbff91b 100644
--- a/content/public/browser/android/synchronous_compositor.h
+++ b/content/public/browser/android/synchronous_compositor.h
@@ -86,10 +86,8 @@ class CONTENT_EXPORT SynchronousCompositor {
       const gfx::Rect& viewport_rect_for_tile_priority,
       const gfx::Transform& transform_for_tile_priority) = 0;
 
-  // Same as DemandDrawHw, but uses asynchronous IPC messages. Calls
-  // SynchronousCompositorClient::OnDrawHardwareProcessFrame to return the
-  // frame.
-  virtual void DemandDrawHwAsync(
+  // Same as DemandDrawHw, but uses asynchronous IPC messages.
+  virtual scoped_refptr<FrameFuture> DemandDrawHwAsync(
       const gfx::Size& viewport_size,
       const gfx::Rect& viewport_rect_for_tile_priority,
       const gfx::Transform& transform_for_tile_priority) = 0;