Introduce ViewRoot to forward input/view events to native

ui/android/view_client.h

+// Copyright 2016 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 UI_ANDROID_VIEW_CLIENT_H_
+#define UI_ANDROID_VIEW_CLIENT_H_
+
+#include "ui/android/ui_android_export.h"
+
+namespace ui {
+
+// Client interface used to forward events from Java to native views.
+// Calls are dispatched to its children along the hierarchy of ViewAndroid.
+// Use bool return type to stop propagating the call i.e. overriden method
+// should return true to indicate that the event was handled and stop
+// the processing.
+class UI_ANDROID_EXPORT ViewClient {
+ public:
+  virtual void OnPhysicalBackingSizeChanged(int width, int height);
+};
+
+}  // namespace ui
+
+#endif  // UI_ANDROID_VIEW_CLIENT_H_