RenderWidget's scheduleComposite should return a bool. (true iff a prompt composite will come).

ui/gfx/compositor/compositor.cc

Index: ui/gfx/compositor/compositor.cc
diff --git a/ui/gfx/compositor/compositor.cc b/ui/gfx/compositor/compositor.cc
index 3a8942a46bc72b742d834a77b51c141e6fba20ed..d4c2cbc91af6bb69f4ad69bc35d02ffc868cac35 100644
--- a/ui/gfx/compositor/compositor.cc
+++ b/ui/gfx/compositor/compositor.cc
@@ -303,8 +303,17 @@ void Compositor::didCompleteSwapBuffers() {
   NotifyEnd();
 }
 
-void Compositor::scheduleComposite() {
+#if defined(WEBLAYERTREEVIEWCLIENT_SCHEDULECOMPOSITE_RETURNS_BOOL)
+#define SCHEDULECOMPOSITE_RETURN_TYPE bool
+#else
+#define SCHEDULECOMPOSITE_RETURN_TYPE void
+#endif
+
+SCHEDULECOMPOSITE_RETURN_TYPE Compositor::scheduleComposite() {
   ScheduleDraw();
+#if defined(WEBLAYERTREEVIEWCLIENT_SCHEDULECOMPOSITE_RETURNS_BOOL)
+  return true;
+#endif
 }
 
 void Compositor::SwizzleRGBAToBGRAAndFlip(unsigned char* pixels,