Issue 11428116 had to be reverted as it broke build due to a unused variable.

chrome/common/extensions/extension.h

 // 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.
 
 #ifndef CHROME_COMMON_EXTENSIONS_EXTENSION_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_H_
 
 #include <algorithm>
 #include <iosfwd>
 #include <map>
@@ skipping 777 matching lines @@
     return (creation_flags_ & WAS_INSTALLED_BY_DEFAULT) != 0;
   }
 
   // App-related.
   bool is_app() const {
     return is_legacy_packaged_app() || is_hosted_app() || is_platform_app();
   }
   bool is_platform_app() const;
   bool is_hosted_app() const;
   bool is_legacy_packaged_app() const;
+  bool is_extension() const;
   bool is_storage_isolated() const { return is_storage_isolated_; }
   bool can_be_incognito_enabled() const;
   const URLPatternSet& web_extent() const { return extent_; }
   const std::string& launch_local_path() const { return launch_local_path_; }
   const std::string& launch_web_url() const { return launch_web_url_; }
   extension_misc::LaunchContainer launch_container() const {
     return launch_container_;
   }
   int launch_width() const { return launch_width_; }
   int launch_height() const { return launch_height_; }
@@ skipping 520 matching lines @@
 
   UpdatedExtensionPermissionsInfo(
       const Extension* extension,
       const PermissionSet* permissions,
       Reason reason);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_H_