Reland of Android: support multiple displays on C++ side

ui/android/dummy_screen_android.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_SCREEN_DUMMY_SCREEN_ANDROID_H_
+#define UI_ANDROID_SCREEN_DUMMY_SCREEN_ANDROID_H_
+
+#include "ui/android/ui_android_export.h"
+
+namespace display {
+class Screen;
+}
+
+namespace ui {
+
+// Creates Screen containing one dummy Display that does not
+// communicate with Java layer.
+UI_ANDROID_EXPORT display::Screen* CreateDummyScreenAndroid();
+
+}  // namespace display
+
+#endif  // UI_ANDROID_SCREEN_DUMMY_SCREEN_ANDROID_H_