Introduce aura::Env controller to abstract away changes to aura::Env

ui/aura/env_input_state_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 UI_AURA_ENV_INPUT_STATE_CONTROLLER_H_
+#define UI_AURA_ENV_INPUT_STATE_CONTROLLER_H_
+
+#include <stdint.h>
+
+#include "base/macros.h"
+#include "ui/aura/aura_export.h"
+
+namespace gfx {
+class Point;
+}
+
+namespace ui {
+class MouseEvent;
+class TouchEvent;
+}
+
+namespace aura {
+
+class Window;
+
+class AURA_EXPORT EnvInputStateController {
+ public:
+  EnvInputStateController() : touch_ids_down_(0) {}
+  ~EnvInputStateController() {}
+
+  void UpdateStateForMouseEvent(const Window* window, ui::MouseEvent* event)
+      const;
+  void UpdateStateForTouchEvent(ui::TouchEvent* event);
+  void SetLastMouseLocation(const Window* root_window,
+                            const gfx::Point& location_in_root) const;
+
+ private:
+  // Touch ids that are currently down.
+  uint32_t touch_ids_down_;
+
+  DISALLOW_COPY_AND_ASSIGN(EnvInputStateController);
+};
+
+}  // namespace aura
+
+#endif  // UI_AURA_ENV_INPUT_STATE_CONTROLLER_H_