Refactor extension app icon.

chrome/browser/extensions/chrome_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_CHROME_APP_ICON_DELEGATE_H_
+#define CHROME_BROWSER_EXTENSIONS_CHROME_APP_ICON_DELEGATE_H_
+
+namespace extensions {
+
+class ChromeAppIcon;
+
+class ChromeAppIconDelegate {
+ public:
+  // Invoked when ChromeAppIcon is updated. "icon->image_skia()" contains

[msw, 2017/05/03 01:17:39]

nit: use vertical bars instead of quotes

[khmel, 2017/05/03 02:15:22]

Done

+  // the current icon image.

[msw, 2017/05/03 01:17:39]

Does current mean the post-update current, or does it mean the prior-to-update
current? Perhaps say "new"/"updated" or "old" instead of current.

[khmel, 2017/05/03 02:15:22]

Done.

+  virtual void OnIconUpdated(ChromeAppIcon* icon) = 0;
+
+ protected:
+  virtual ~ChromeAppIconDelegate() {}
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_CHROME_APP_ICON_DELEGATE_H_