Forward handling of low-mem message to the content renderer client. Add APIs to handle this case.

chrome/renderer/chrome_render_process_observer.h

 // Copyright (c) 2011 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_RENDERER_CHROME_RENDER_PROCESS_OBSERVER_H_
 #define CHROME_RENDERER_CHROME_RENDER_PROCESS_OBSERVER_H_
 #pragma once
 
 #include <string>
 
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
+#include "content/common/notification_observer.h"
+#include "content/common/notification_registrar.h"
 #include "content/renderer/render_process_observer.h"
 
 class GURL;
 class ResourceDispatcherDelegate;
 struct ContentSettings;
 
 // This class filters the incoming control messages (i.e. ones not destined for
 // a RenderView) for Chrome specific messages that the content layer doesn't
 // happen.  If a few messages are related, they should probably have their own
 // observer.
-class ChromeRenderProcessObserver : public RenderProcessObserver {
+class ChromeRenderProcessObserver : public RenderProcessObserver,
+                                    public NotificationObserver {
  public:
   ChromeRenderProcessObserver();
   virtual ~ChromeRenderProcessObserver();
 
   static bool is_incognito_process() { return is_incognito_process_; }
 
+  // NotificationObserver
+  void Observe(int type,
+               const NotificationSource& source,
+               const NotificationDetails& details) OVERRIDE;
+
  private:
   // RenderProcessObserver implementation.
   virtual bool OnControlMessageReceived(const IPC::Message& message) OVERRIDE;
   virtual void WebKitInitialized() OVERRIDE;
 
   void OnSetIsIncognitoProcess(bool is_incognito_process);
   void OnSetContentSettingsForCurrentURL(
       const GURL& url, const ContentSettings& content_settings);
   void OnSetDefaultContentSettings(const ContentSettings& content_settings);
   void OnSetCacheCapacities(size_t min_dead_capacity,
                             size_t max_dead_capacity,
                             size_t capacity);
   void OnClearCache();
   void OnGetCacheResourceStats();
   void OnSetFieldTrialGroup(const std::string& fiel_trial_name,
                             const std::string& group_name);
   void OnGetRendererTcmalloc();
   void OnGetV8HeapStats();
   void OnPurgeMemory();
 
   static bool is_incognito_process_;
   scoped_ptr<ResourceDispatcherDelegate> resource_delegate_;
 
+  NotificationRegistrar registrar_;
+
   DISALLOW_COPY_AND_ASSIGN(ChromeRenderProcessObserver);
 };
 
 #endif  // CHROME_RENDERER_CHROME_RENDER_PROCESS_OBSERVER_H_