linux: turn on -Wextra

chrome/common/extensions/extension.h

 // Copyright (c) 2010 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_COMMON_EXTENSIONS_EXTENSION_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_H_
 
 #include <map>
 #include <set>
 #include <string>
@@ skipping 286 matching lines @@
   // Chrome URL overrides (see ExtensionOverrideUI).
   const URLOverrideMap& GetChromeURLOverrides() const {
     return chrome_url_overrides_;
   }
 
   bool web_content_enabled() const { return web_content_enabled_; }
   const ExtensionExtent& web_extent() const { return web_extent_; }
 
   const std::string& launch_local_path() const { return launch_local_path_; }
   const std::string& launch_web_url() const { return launch_web_url_; }
-  const LaunchContainer launch_container() const { return launch_container_; }
+  LaunchContainer launch_container() const { return launch_container_; }
 
   // Gets the fully resolved absolute launch URL.
   GURL GetFullLaunchURL() const;
 
   // Runtime data:
   // Put dynamic data about the state of a running extension below.
 
   // Whether the background page, if any, is ready. We don't load other
   // components until then. If there is no background page, we consider it to
   // be ready.
@@ skipping 194 matching lines @@
   scoped_ptr<DictionaryValue> extension_manifest;
   std::string extension_id;
   FilePath extension_path;
   Extension::Location extension_location;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ExtensionInfo);
 };
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_H_