Delay Input.dispatchKeyEvent response until after key event ack.

content/public/browser/render_widget_host.h

Index: content/public/browser/render_widget_host.h
diff --git a/content/public/browser/render_widget_host.h b/content/public/browser/render_widget_host.h
index f8bf0927032122249ad8c1a8c0e8778adacc60d4..9fb1e0b4b718d39cd775c98de7abb3a84932e5f2 100644
--- a/content/public/browser/render_widget_host.h
+++ b/content/public/browser/render_widget_host.h
@@ -240,12 +240,18 @@ class CONTENT_EXPORT RenderWidgetHost : public IPC::Sender {
   virtual void AddMouseEventCallback(const MouseEventCallback& callback) = 0;
   virtual void RemoveMouseEventCallback(const MouseEventCallback& callback) = 0;
 
-  // Observer for WebInputEvents (but not input event acks).
+  // Observer for WebInputEvents.
   class InputEventObserver {
    public:
     virtual ~InputEventObserver() {}
 
     virtual void OnInputEvent(const blink::WebInputEvent&) = 0;
+
+    // Called when the browser process receives an ack from the render process.
+    // |is_synthetic| is true if the event was generated by DevTools, rather
+    // than in response to user input.
+    virtual void OnInputEventAck(const blink::WebInputEvent& event,
+                                 bool is_synthetic) = 0;
   };
 
   // Add/remove an input event observer.