sync compositor: Signal async frame on IO thread

android_webview/browser/render_thread_manager.h

Index: android_webview/browser/render_thread_manager.h
diff --git a/android_webview/browser/render_thread_manager.h b/android_webview/browser/render_thread_manager.h
index e23b2c24841f6bccf650c32b6b49aca632fff085..ca9e4b314f109478836d7f8c1707963d17c1b7da 100644
--- a/android_webview/browser/render_thread_manager.h
+++ b/android_webview/browser/render_thread_manager.h
@@ -63,6 +63,8 @@ class RenderThreadManager : public CompositorFrameConsumer {
   // RT thread methods.

[dcheng, 2016/10/21 06:42:56]

Nit: Perhaps expand "RT" here (I assume RT = RenderThread, but that means this
comment then reads RenderThread thread methods)

[boliu, 2016/10/21 15:15:32]

Yep. Updated to "Render thread methods"

   gfx::Vector2d GetScrollOffsetOnRT();
   std::unique_ptr<ChildFrame> PassFrameOnRT();
+  scoped_refptr<content::SynchronousCompositor::FrameFuture>
+  PassFrameFutureOnRT();
   void DrawGL(AwDrawGLInfo* draw_info);
   void PostExternalDrawConstraintsToChildCompositorOnRT(
       const ParentCompositorDrawConstraints& parent_draw_constraints);