Refactor extension app icon.

chrome/browser/extensions/extension_app_icon_delegate.h

+// Copyright 2017 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_BROWSER_EXTENSIONS_EXTENSION_APP_ICON_DELEGATE_H_
+#define CHROME_BROWSER_EXTENSIONS_EXTENSION_APP_ICON_DELEGATE_H_
+
+namespace gfx {
+class ImageSkia;
+};
+
+namespace extensions {
+
+class ExtensionAppIcon;
+
+class ExtensionAppIconDelegate {
+ public:
+  virtual void UpdateIcon(ExtensionAppIcon* icon,

[xiyuan, 2017/04/18 20:43:00]

Document the method. 

  // Invoked when ExtensionAppIcon is updated.

And this makes me feel the function should probably be called OnIconUpdated.

[khmel, 2017/04/20 00:13:38]

Done.

+                          const gfx::ImageSkia& image) = 0;

[xiyuan, 2017/04/18 20:43:00]

nit: Shouldn't |image| be part of |icon|? i.e. expose |image| from |icon|.

[khmel, 2017/04/20 00:13:38]

Makes sense. this gives more flexibility in using.

+
+ protected:
+  virtual ~ExtensionAppIconDelegate() {}
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_APP_ICON_DELEGATE_H_