Made return types of various Value::DeepCopy() implementations more specific

chrome/browser/extensions/external_pref_extension_loader.cc

 // 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.
 
 #include "chrome/browser/extensions/external_pref_extension_loader.h"
 
 #include "app/app_paths.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/logging.h"
@@ skipping 58 matching lines @@
 
 ExternalTestingExtensionLoader::ExternalTestingExtensionLoader(
     const std::string& json_data) {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   JSONStringValueSerializer serializer(json_data);
   testing_prefs_.reset(ExtractPrefs(&serializer));
 }
 
 void ExternalTestingExtensionLoader::StartLoading() {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  prefs_.reset(
-      static_cast<DictionaryValue*>(testing_prefs_->DeepCopy()));
+  prefs_.reset(testing_prefs_->DeepCopy());
   LoadFinished();
 }