Cleanup: Remove unneeded forward declarations from various chrome/browser subdirectories.

chrome/browser/download/download_extension_api.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_DOWNLOAD_DOWNLOAD_EXTENSION_API_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_EXTENSION_API_H_
 #pragma once
 
 #include <map>
 #include <set>
 #include <string>
 
 #include "base/file_path.h"
 #include "base/memory/singleton.h"
 #include "base/string16.h"
 #include "chrome/browser/extensions/extension_function.h"
 #include "content/browser/download/download_item.h"
 #include "content/browser/download/download_manager.h"
 
-namespace base {
-class DictionaryValue;
-}
 class ResourceDispatcherHost;
-class TabContents;
+
 namespace content {
 class ResourceContext;
 }
 
 // Functions in the chrome.experimental.downloads namespace facilitate
 // controlling downloads from extensions. See the full API doc at
 // http://goo.gl/6hO1n
 
 class DownloadsFunctionInterface {
  public:
@@ skipping 233 matching lines @@
   typedef base::hash_map<int, DownloadItem*> ItemMap;
   typedef std::set<int> DownloadIdSet;
 
   Profile* profile_;
   DownloadManager* manager_;
   DownloadIdSet downloads_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionDownloadsEventRouter);
 };
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_EXTENSION_API_H_