Generalize ExtensionIconSet to store icon paths for custom size sets

chrome/common/extensions/extension_constants.h

Index: chrome/common/extensions/extension_constants.h
diff --git a/chrome/common/extensions/extension_constants.h b/chrome/common/extensions/extension_constants.h
index bec8414e850b2d8ec8a3e214181a8f67bb04aa12..1aec6b15842cfd73fc2fe5eb907e77f4d55cfab0 100644
--- a/chrome/common/extensions/extension_constants.h
+++ b/chrome/common/extensions/extension_constants.h
@@ -244,6 +244,11 @@ namespace extension_misc {
   // 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_