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 {

[msw, 2017/05/08 19:59:53]

Why is this needed? Why not just pass the AppIconLoaderDelegate from
ChromeAppIconLoader to ChromeAppIcon and have that call OnAppImageUpdated
directly, instead of introducing an intermediary delegate interface?

[khmel, 2017/05/09 00:05:04]

AppIconLoaderDelegate is only once case how to use it. There are consumers that
use ChromeAppIcon directly. ChromeAppIconLoader is helper class for some but not
for all use cases.

[msw, 2017/05/10 19:05:21]

Right, but it's *so* similar (just one On[Icon|AppImage]Updated function), why
not just re-use the AppIconLoaderDelegate interface, even if you have to
maintain separate icon/loader and icon/service clients? The ExtensionAppItem,
ExtensionAppResult, and AppInfoHeaderPanel overrides for
AppIconLoaderDelegate::OnAppImageUpdated could even include a comment that says
"This is called by ChromeAppIconService when the ChromeAppIcon is updated, even
though this class doesn't directly use a ChromeAppIconLoader." (or similar) if
you feel that is necessary.

[khmel, 2017/05/11 02:13:48]

As agreed, I will remove AppIconloader and from this point of view 
AppIconloaderDelegate will go away also. So IIUC it is better to leave this
file.

+ public:
+  // Invoked when ChromeAppIcon is updated. |icon->image_skia()| contains
+  // the update icon image with applied effects.
+  virtual void OnIconUpdated(ChromeAppIcon* icon) = 0;
+
+ protected:
+  virtual ~ChromeAppIconDelegate() {}
+};
+
+}  // namespace extensions
+
+#endif  // CHROME_BROWSER_EXTENSIONS_CHROME_APP_ICON_DELEGATE_H_