Delay Input.dispatchKeyEvent response until after key event ack.

chrome/browser/metrics/desktop_session_duration/desktop_session_duration_observer.h

 // Copyright 2016 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_METRICS_DESKTOP_SESSION_DURATION_DESKTOP_SESSION_DURATION_OBSERVER_H_
 #define CHROME_BROWSER_METRICS_DESKTOP_SESSION_DURATION_DESKTOP_SESSION_DURATION_OBSERVER_H_
 
 #include "base/macros.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/web_contents.h"
@@ skipping 21 matching lines @@
 
  private:
   friend class content::WebContentsUserData<DesktopSessionDurationObserver>;
 
   // Register / Unregister input event callback to given RenderViewHost
   void RegisterInputEventObserver(content::RenderViewHost* host);
   void UnregisterInputEventObserver(content::RenderViewHost* host);
 
   // content::RenderWidgetHost::InputEventObserver:
   void OnInputEvent(const blink::WebInputEvent& event) override;
+  void OnInputEventAck(const blink::WebInputEvent& event) override {};
 
   // content::WebContentsObserver:
   void RenderViewHostChanged(content::RenderViewHost* old_host,
                              content::RenderViewHost* new_host) override;
 
   DesktopSessionDurationTracker* service_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopSessionDurationObserver);
 };
 
 }  // namespace metrics
 
 #endif  // CHROME_BROWSER_METRICS_DESKTOP_SESSION_DURATION_DESKTOP_SESSION_DURATION_OBSERVER_H_