Implemented the rest of loading/parsing logic for extension i18n:...

chrome/browser/extensions/extension_l10n_util.h

 // Copyright (c) 2009 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.
 //
 // This file declares extension specific l10n utils.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_EXTENSION_L10N_UTIL_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_L10N_UTIL_H_
 
 #include <set>
@@ skipping 23 matching lines @@
 // 1. Do nothing if _locales directory is missing (not an error).
 // 2. Get list of Chrome locales.
 // 3. Enumerate all subdirectories of _locales directory.
 // 4. Intersect both lists, and add intersection to the extension.
 // Returns false if any of supplied locales don't match chrome list of locales.
 // Fills out error with offending locale name.
 bool AddValidLocales(const FilePath& locale_path,
                      Extension* extension,
                      std::string* error);
 
+// Loads messages file for default locale, and application locale (application
+// locale doesn't have to exist).
+// It creates simplified in-memory representation of name-value pairs, where
+// value part is actual message with placeholders resolved.
+// Returns true if it can load default locale messages file, and all messages
+// are valid.
+bool LoadMessageCatalogs(const FilePath& locale_path,
+                         Extension* extension,
+                         std::string* error);
+
 }  // namespace extension_l10n_util
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_L10N_UTIL_H_