Delay Input.dispatchKeyEvent response until after key event ack.

chrome/browser/page_load_metrics/metrics_web_contents_observer.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_PAGE_LOAD_METRICS_METRICS_WEB_CONTENTS_OBSERVER_H_
 #define CHROME_BROWSER_PAGE_LOAD_METRICS_METRICS_WEB_CONTENTS_OBSERVER_H_
 
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 42 matching lines @@
 
   // content::WebContentsObserver implementation:
   bool OnMessageReceived(const IPC::Message& message,
                          content::RenderFrameHost* render_frame_host) override;
   void DidFinishNavigation(
       content::NavigationHandle* navigation_handle) override;
   void DidRedirectNavigation(
       content::NavigationHandle* navigation_handle) override;
   void NavigationStopped() override;
   void OnInputEvent(const blink::WebInputEvent& event) override;
+  void OnInputEventAck(const blink::WebInputEvent& event) override {};
   void WasShown() override;
   void WasHidden() override;
   void RenderProcessGone(base::TerminationStatus status) override;
   void RenderViewHostChanged(content::RenderViewHost* old_host,
                              content::RenderViewHost* new_host) override;
 
   // This method is forwarded from the MetricsNavigationThrottle.
   void WillStartNavigationRequest(content::NavigationHandle* navigation_handle);
 
   // A resource request completed on the IO thread.
@@ skipping 72 matching lines @@
 
   // Has the MWCO observed at least one navigation?
   bool has_navigated_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsWebContentsObserver);
 };
 
 }  // namespace page_load_metrics
 
 #endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_METRICS_WEB_CONTENTS_OBSERVER_H_