Move CrxFile, FileReader, ExtensionResource to src/extensions.

extensions/common/constants.cc

 // Copyright (c) 2012 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 "extensions/common/constants.h"
 
 namespace extensions {
 
 const char kExtensionScheme[] = "chrome-extension";
 
+const base::FilePath::CharType kManifestFilename[] =
+    FILE_PATH_LITERAL("manifest.json");
+const base::FilePath::CharType kLocaleFolder[] =
+    FILE_PATH_LITERAL("_locales");
+const base::FilePath::CharType kMessagesFilename[] =
+    FILE_PATH_LITERAL("messages.json");
+const base::FilePath::CharType kPlatformSpecificFolder[] =
+    FILE_PATH_LITERAL("_platform_specific");
+
 } // namespace extensions