Attempt four at landing the "histogram.h removed from message_loop.h" patch.

chrome/browser/plugin_service.h

 // 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.
 
 // This class responds to requests from renderers for the list of plugins, and
 // also a proxy object for plugin instances.
 
 #ifndef CHROME_BROWSER_PLUGIN_SERVICE_H_
 #define CHROME_BROWSER_PLUGIN_SERVICE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/hash_tables.h"
 #include "base/ref_counted.h"
 #include "base/singleton.h"
 #include "base/waitable_event_watcher.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/common/notification_observer.h"
 #include "chrome/common/notification_registrar.h"
 #include "googleurl/src/gurl.h"
 
 #if defined(OS_WIN)
 #include "base/registry.h"
+#include "base/scoped_ptr.h"
 #endif
 
 namespace IPC {
 class Message;
 }
 
 class MessageLoop;
 class PluginProcessHost;
 class Profile;
 class URLRequestContext;
@@ skipping 116 matching lines @@
   base::WaitableEventWatcher hklm_watcher_;
 #endif
 
   // Set to true if chrome plugins are enabled. Defaults to true.
   static bool enable_chrome_plugins_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginService);
 };
 
 #endif  // CHROME_BROWSER_PLUGIN_SERVICE_H_