ash: Refactor touch hud drawing to ash/touch_hud as a separate component.

ui/views/controls/touch/touch_hud_drawer.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_VIEWS_CONTROLS_TOUCH_TOUCH_HUD_DRAWER_H_
+#define UI_VIEWS_CONTROLS_TOUCH_TOUCH_HUD_DRAWER_H_
+
+#include <map>
+#include <memory>
+
+#include "base/macros.h"
+#include "ui/views/views_export.h"
+
+namespace ash {
+class TouchHudProjectionTest;
+}
+
+namespace ui {
+class LocatedEvent;
+}
+
+namespace views {
+class TouchPointView;
+class Widget;
+
+// Handles touch events to draw out touch points accordingly.
+class VIEWS_EXPORT TouchHudDrawer {

[sky, 2016/07/07 00:04:38]

Can I also suggest naming this TouchHudRenderer? Drawer makes me think of a
place I put my clothes:)

[riajiang, 2016/07/11 16:26:03]

Done :)

+ public:
+   static std::unique_ptr<TouchHudDrawer> Get();

[sky, 2016/07/07 00:04:38]

Why do you need a Get() that uses the constructor when the constructor is
public? Also, if you do really need this function it should be after the
constructor/destructor (see style guide) and I would name it Create() as that is
what it is doing. But again, it seems like callers can just create directly.

[riajiang, 2016/07/11 16:26:03]

Changed it back. I was trying to convert it to a unique_ptr in Get/Create. Now
moved it to when I need to own this as a unique_ptr (touch_hud_projection)

+
+   TouchHudDrawer();
+   ~TouchHudDrawer();
+
+  // Called to clear touch points and traces from the screen.
+  void Clear();
+
+  // Receives a touch event and draws its touch point under parent_widget.
+  void HandleTouchEvent(const ui::LocatedEvent* event, Widget* parent_widget);
+
+ private:
+  friend class ash::TouchHudProjectionTest;
+
+  // a map of touch ids to TouchPointView
+  std::map<int, TouchPointView*> points_;
+
+  DISALLOW_COPY_AND_ASSIGN(TouchHudDrawer);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_CONTROLS_TOUCH_TOUCH_HUD_DRAWER_H_