[Android] Embedding API: XWalkUIClient.onIconAvailable

This commit implements API of onReceivedIcon and onIconAvailable
```
// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Copyright (c) 2014 Intel Corporation. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
```