Fix uninitialized value in SiteEngagementHelper.

chrome/browser/engagement/site_engagement_helper.cc

 // 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.
 
 #include "chrome/browser/engagement/site_engagement_helper.h"
 
 #include <utility>
 
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 50 matching lines @@
     base::TimeDelta delay) {
   pause_timer_->Start(
       FROM_HERE, delay,
       base::Bind(&SiteEngagementHelper::PeriodicTracker::TrackingStarted,
                  base::Unretained(this)));
 }
 
 SiteEngagementHelper::InputTracker::InputTracker(
     SiteEngagementHelper* helper,
     content::WebContents* web_contents)
-    : PeriodicTracker(helper), content::WebContentsObserver(web_contents) {}
+    : PeriodicTracker(helper),
+      content::WebContentsObserver(web_contents),
+      is_tracking_(false) {}
 
 void SiteEngagementHelper::InputTracker::TrackingStarted() {
   is_tracking_ = true;
 }
 
 void SiteEngagementHelper::InputTracker::TrackingStopped() {
   is_tracking_ = false;
 }
 
 // Record that there was some user input, and defer handling of the input event.
@@ skipping 177 matching lines @@
 
 // static
 void SiteEngagementHelper::SetSecondsTrackingDelayAfterNavigation(int seconds) {
   g_seconds_delay_after_navigation = seconds;
 }
 
 // static
 void SiteEngagementHelper::SetSecondsTrackingDelayAfterShow(int seconds) {
   g_seconds_delay_after_show = seconds;
 }