Add a preference to clear plugin data on browser shutdown.

chrome/browser/plugin_data_remover_helper.cc

 // Copyright (c) 2010 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/plugin_data_remover_helper.h"
 
 #include "base/ref_counted.h"
 #include "chrome/browser/browser_thread.h"
 #include "chrome/browser/plugin_data_remover.h"
 #include "chrome/common/notification_service.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
 
+// The internal class is refcounted so it can outlive PluginDataRemoverHelper.
 class PluginDataRemoverHelper::Internal
     : public base::RefCountedThreadSafe<PluginDataRemoverHelper::Internal> {
  public:
   explicit Internal(const char* pref_name, PrefService* prefs)
       : pref_name_(pref_name), prefs_(prefs) {}
 
   void StartUpdate() {
     BrowserThread::PostTask(
         BrowserThread::FILE,
         FROM_HERE,
@@ skipping 55 matching lines @@
 
 void PluginDataRemoverHelper::Observe(NotificationType type,
                                       const NotificationSource& source,
                                       const NotificationDetails& details) {
   if (type.value == NotificationType::PLUGIN_ENABLE_STATUS_CHANGED) {
     internal_->StartUpdate();
   } else {
     NOTREACHED();
   }
 }