Generalize ExtensionIconSet to store icon paths for custom size sets

chrome/common/extensions/extension_constants.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_CONSTANTS_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 226 matching lines @@
   extern const char kAppStateRunning[];
   extern const char kAppStateCannotRun[];
   extern const char kAppStateReadyToRun[];
 
   // The path part of the file system url used for media file systems.
   extern const char kMediaFileSystemPathPart[];
 
   // Error indicating that the app notifications API is not accessible by split
   // mode extensions in incognito windows.
   extern const char kAppNotificationsIncognitoError[];
+
+  // List of sizes for extension icons that can be defined in the manifest.
+  extern const int kExtensionIconSizes[];
+  extern const size_t kNumExtensionIconSizes;
+
 }  // extension_misc
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_