Fix crash in SiteEngagementServiceHelper when switching render view hosts.

chrome/browser/engagement/site_engagement_helper.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_ENGAGEMENT_SITE_ENGAGEMENT_HELPER_H_
 #define CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_HELPER_H_
 
 #include "base/macros.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/engagement/site_engagement_metrics.h"
@@ skipping 60 matching lines @@
 
     // Switches the InputTracker to another RenderViewHost, respecting the pause
     // timer state.
     void SwitchRenderViewHost(content::RenderViewHost* old_host,
                               content::RenderViewHost* new_host);
 
     // Stop listening for user input.
     void Stop();
 
     // Returns whether the InputTracker has been started for a RenderViewHost.
-    bool is_active() const { return is_active_; }
+    bool IsActive() const;
 
     // Returns whether input tracking callbacks have been added to
     // RenderViewHost.
     bool is_tracking() const { return is_tracking_; }
 
+    content::RenderViewHost* host() const { return host_; }
+
     // Set the timer object for testing purposes.
     void SetPauseTimerForTesting(scoped_ptr<base::Timer> timer);
 
    private:
     // Starts the timer for adding callbacks to the RenderViewHost.
     void StartTimer(base::TimeDelta delay);
 
     // Adds/removes tracking callbacks to the RenderViewHost.
     void AddCallbacks();
     void RemoveCallbacks();
 
     SiteEngagementHelper* helper_;
     scoped_ptr<base::Timer> pause_timer_;
     content::RenderViewHost* host_;
     content::RenderWidgetHost::KeyPressEventCallback key_press_event_callback_;
     content::RenderWidgetHost::MouseEventCallback mouse_event_callback_;
-    bool is_active_;
     bool is_tracking_;
   };
 
   explicit SiteEngagementHelper(content::WebContents* web_contents);
   friend class content::WebContentsUserData<SiteEngagementHelper>;
   friend class SiteEngagementServiceBrowserTest;
 
   // Ask the SiteEngagementService to record engagement via user input at the
   // current contents location.
   void RecordUserInput(SiteEngagementMetrics::EngagementType type);
 
   InputTracker input_tracker_;
   bool record_engagement_;
 
   DISALLOW_COPY_AND_ASSIGN(SiteEngagementHelper);
 };
 
 #endif  // CHROME_BROWSER_ENGAGEMENT_SITE_ENGAGEMENT_HELPER_H_