Cleanup: Remove more forward declarations in various chrome/browser directories.

chrome/browser/plugin_data_remover.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_BROWSER_PLUGIN_DATA_REMOVER_H_
 #define CHROME_BROWSER_PLUGIN_DATA_REMOVER_H_
 #pragma once
 
+#include <string>
+
 #include "base/memory/ref_counted.h"
 #include "base/time.h"
 #include "content/browser/plugin_process_host.h"
 
 class PluginPrefs;
 class Profile;
-class Task;
 
 namespace base {
-class MessageLoopProxy;
 class WaitableEvent;
 }
 
 class PluginDataRemover : public base::RefCountedThreadSafe<PluginDataRemover>,
                           public PluginProcessHost::Client,
                           public IPC::Channel::Listener {
  public:
   explicit PluginDataRemover(Profile* profile);
 
   // The plug-in whose data should be removed (usually Flash) is specified via
@@ skipping 58 matching lines @@
   scoped_ptr<base::WaitableEvent> event_;
   // We own the channel, but it's used on the IO thread, so it needs to be
   // deleted there. It's NULL until we have opened a connection to the plug-in
   // process.
   IPC::Channel* channel_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginDataRemover);
 };
 
 #endif  // CHROME_BROWSER_PLUGIN_DATA_REMOVER_H_