sync compositor: Signal async frame on IO thread

android_webview/browser/hardware_renderer.h

Index: android_webview/browser/hardware_renderer.h
diff --git a/android_webview/browser/hardware_renderer.h b/android_webview/browser/hardware_renderer.h
index 2a83fda458979ced8db845aef86fba2e7faab083..8819f86fdaa48edc27129f9a0552ada2d702aa25 100644
--- a/android_webview/browser/hardware_renderer.h
+++ b/android_webview/browser/hardware_renderer.h
@@ -13,6 +13,7 @@
 #include "cc/surfaces/frame_sink_id.h"
 #include "cc/surfaces/surface_factory_client.h"
 #include "cc/surfaces/surface_id.h"
+#include "content/public/browser/android/synchronous_compositor.h"
 
 struct AwDrawGLInfo;
 
@@ -66,6 +67,8 @@ class HardwareRenderer : public cc::SurfaceFactoryClient {
   // SurfaceFactory.
   std::unique_ptr<ChildFrame> child_frame_;
 
+  scoped_refptr<content::SynchronousCompositor::FrameFuture> frame_future_;
+
   const scoped_refptr<SurfacesInstance> surfaces_;
   cc::FrameSinkId frame_sink_id_;
   const std::unique_ptr<cc::SurfaceIdAllocator> surface_id_allocator_;