Enqueuing new frames in a Surface should cause Displays to reaggregate it

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index 0e4ac8a0a27e261c3955f368f8a09976029c3193..bfc0ce2c39e4f8d60485ba2d3cb3c38ee9586e7f 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -192,6 +192,12 @@ class COMPOSITOR_EXPORT Compositor
   // Returns the vsync manager for this compositor.
   scoped_refptr<CompositorVSyncManager> vsync_manager() const;
 
+  // Returns the main thread task runner this compositor uses. Users of the
+  // compositor generally shouldn't use this.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner() const {
+    return task_runner_;
+  }
+
   // Compositor does not own observers. It is the responsibility of the
   // observer to remove itself when it is done observing.
   void AddObserver(CompositorObserver* observer);