Implement rudimentary touchscreen support in mus.

components/mus/ws/touch_controller.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 COMPONENTS_MUS_WS_TOUCH_CONTROLLER_H_
+#define COMPONENTS_MUS_WS_TOUCH_CONTROLLER_H_
+
+#include "base/macros.h"
+#include "ui/events/devices/input_device_event_observer.h"
+
+namespace mus {
+namespace ws {
+
+class DisplayManager;
+
+// Tracks changes to displays and touchscreen devices. Updates the mapping
+// between display devices and touchscreen devices when changes occur.
+class TouchController : public ui::InputDeviceEventObserver {
+ public:
+  explicit TouchController(DisplayManager* display_manager);
+  ~TouchController() override;
+
+  void UpdateTouchTransforms() const;
+
+  // ui::InputDeviceEventObserver:
+  void OnTouchscreenDeviceConfigurationChanged() override;
+
+ private:
+  DisplayManager* display_manager_;
+
+  DISALLOW_COPY_AND_ASSIGN(TouchController);
+};
+
+}  // namespace ws
+}  // namespace mus
+
+#endif  // COMPONENTS_MUS_WS_TOUCH_CONTROLLER_H_