Cleanup: Remove unneeded forward declarations from various chrome subdirectories.

chrome/default_plugin/plugin_impl_mac.h

-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// 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_DEFAULT_PLUGIN_PLUGIN_IMPL_MAC_H_
 #define CHROME_DEFAULT_PLUGIN_PLUGIN_IMPL_MAC_H_
 #pragma once
 
 #include <string>
 
 #include "chrome/default_plugin/plugin_installer_base.h"
@@ skipping 15 matching lines @@
   PluginListDownloaded,
   PluginListDownloadedPluginNotFound,
   PluginListDownloadFailed,
   PluginDownloadInitiated,
   PluginDownloadCompleted,
   PluginDownloadFailed,
   PluginInstallerLaunchSuccess,
   PluginInstallerLaunchFailure
 };
 
-class PluginInstallDialog;
-class PluginDatabaseHandler;
-
 // Provides the plugin installation functionality. This class is
 // instantiated with the information like the mime type of the
 // target plugin, the display mode, etc.
 class PluginInstallerImpl : public PluginInstallerBase {
  public:
   // mode is the plugin instantiation mode, i.e. whether it is a full
   // page plugin (NP_FULL) or an embedded plugin (NP_EMBED)
   explicit PluginInstallerImpl(int16 mode);
   virtual ~PluginInstallerImpl();
 
@@ skipping 239 matching lines @@
   // Plugin icon, weak (owned by ResourceBundle).
   NSImage* image_;
   // Displayed text
   NSString* command_;
 
   DISALLOW_COPY_AND_ASSIGN(PluginInstallerImpl);
 };
 
 
 #endif  // CHROME_DEFAULT_PLUGIN_PLUGIN_IMPL_MAC_H_