Fix crash in SiteEngagementServiceHelper when switching render view hosts.

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 "base/time/time.h"
 #include "base/trace_event/trace_event.h"
 #include "chrome/browser/engagement/site_engagement_service.h"
 #include "chrome/browser/engagement/site_engagement_service_factory.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/profiles/profile.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/web_contents.h"
 
 namespace {
 
 int g_seconds_between_user_input_check = 10;
 int g_seconds_tracking_delay_after_navigation = 10;
 int g_seconds_tracking_delay_after_show = 5;
 
 }  // anonymous namespace
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(SiteEngagementHelper);
 
 SiteEngagementHelper::InputTracker::InputTracker(SiteEngagementHelper* helper)
     : helper_(helper),
       pause_timer_(new base::Timer(true, false)),
       host_(nullptr),
-      is_active_(false),
       is_tracking_(false) {
   key_press_event_callback_ =
       base::Bind(&SiteEngagementHelper::InputTracker::HandleKeyPressEvent,
                  base::Unretained(this));
   mouse_event_callback_ =
       base::Bind(&SiteEngagementHelper::InputTracker::HandleMouseEvent,
                  base::Unretained(this));
 }
 
 SiteEngagementHelper::InputTracker::~InputTracker() {}
@@ skipping 23 matching lines @@
        event.type == blink::WebInputEvent::MouseDown) ||
       event.type == blink::WebInputEvent::MouseWheel) {
     Pause();
     helper_->RecordUserInput(SiteEngagementMetrics::ENGAGEMENT_MOUSE);
   }
   return false;
 }
 
 void SiteEngagementHelper::InputTracker::Start(content::RenderViewHost* host,
                                                base::TimeDelta initial_delay) {
-  DCHECK(!is_active_);
+  DCHECK(!host_);
   DCHECK(host);
   host_ = host;
   StartTimer(initial_delay);
-  is_active_ = true;
 }
 
 void SiteEngagementHelper::InputTracker::Pause() {
   RemoveCallbacks();
   StartTimer(base::TimeDelta::FromSeconds(g_seconds_between_user_input_check));
 }
 
 void SiteEngagementHelper::InputTracker::SwitchRenderViewHost(
     content::RenderViewHost* old_host,
     content::RenderViewHost* new_host) {
-  DCHECK(is_tracking_);
+  DCHECK(host_);
   DCHECK(new_host);
 
   bool was_tracking = is_tracking_;
   if (old_host) {
     DCHECK_EQ(host_, old_host);
     RemoveCallbacks();
   }
 
   host_ = new_host;
 
   if (was_tracking)
     AddCallbacks();
 }
 
 void SiteEngagementHelper::InputTracker::Stop() {
   pause_timer_->Stop();
   RemoveCallbacks();
   host_ = nullptr;
-  is_active_ = false;
+}
+
+bool SiteEngagementHelper::InputTracker::IsActive() const {
+  return host_ != nullptr;
 }
 
 void SiteEngagementHelper::InputTracker::SetPauseTimerForTesting(
     scoped_ptr<base::Timer> timer) {
   pause_timer_ = timer.Pass();
 }
 
 void SiteEngagementHelper::InputTracker::StartTimer(base::TimeDelta delay) {
   pause_timer_->Start(
       FROM_HERE, delay,
@@ skipping 68 matching lines @@
   input_tracker_.Start(
       web_contents()->GetRenderViewHost(),
       base::TimeDelta::FromSeconds(g_seconds_tracking_delay_after_navigation));
 }
 
 void SiteEngagementHelper::RenderViewHostChanged(
     content::RenderViewHost* old_host,
     content::RenderViewHost* new_host) {
   // On changing the render view host, we need to re-register the callbacks
   // listening for user input.
-  if (input_tracker_.is_tracking()) {
+  if (input_tracker_.IsActive()) {
     input_tracker_.SwitchRenderViewHost(old_host, new_host);
   }
 }
 
 void SiteEngagementHelper::WasShown() {
   // Ensure that the input callbacks are registered when we come into view.
   if (record_engagement_) {
     input_tracker_.Start(
         web_contents()->GetRenderViewHost(),
         base::TimeDelta::FromSeconds(g_seconds_tracking_delay_after_show));
@@ skipping 12 matching lines @@
 
 // static
 void SiteEngagementHelper::SetSecondsTrackingDelayAfterNavigation(int seconds) {
   g_seconds_tracking_delay_after_navigation = seconds;
 }
 
 // static
 void SiteEngagementHelper::SetSecondsTrackingDelayAfterShow(int seconds) {
   g_seconds_tracking_delay_after_show = seconds;
 }