Move ".crx"/".pem" constants and extension_filenames constants into extensions/common/constants.cc.

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 "base/files/file_path.h"
 #include "extensions/common/constants.h"
 
 namespace extensions {
 
 const char kExtensionScheme[] = "chrome-extension";
 
+namespace filenames {
+
 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");
 
 const char kInstallDirectoryName[] = "Extensions";
 
-} // namespace extensions
+const char kTempExtensionName[] = "CRX_INSTALL";
+const char kDecodedImagesFilename[] = "DECODED_IMAGES";
+const char kDecodedMessageCatalogsFilename[] = "DECODED_MESSAGE_CATALOGS";
+const char kGeneratedBackgroundPageFilename[] =
+    "_generated_background_page.html";
+const char kModulesDir[] = "_modules";
+
+const base::FilePath::CharType kExtensionFileExtension[] =
+    FILE_PATH_LITERAL(".crx");
+const base::FilePath::CharType kExtensionKeyFileExtension[] =
+    FILE_PATH_LITERAL(".pem");
+
+bool IsExtension(const base::FilePath& file_name) {
+  return file_name.MatchesExtension(kExtensionFileExtension);
+}
+
+}  // namespace filenames
+
+}  // namespace extensions