Allow taking screen shot of a non child window which has delegate to paint.

ash/utility/partial_screenshot_controller.h

-// Copyright 2014 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 ASH_UTILITY_PARTIAL_SCREENSHOT_CONTROLLER_H_
-#define ASH_UTILITY_PARTIAL_SCREENSHOT_CONTROLLER_H_
-
-#include <stdint.h>
-
-#include <map>
-#include <memory>
-
-#include "ash/ash_export.h"
-#include "ash/shell_observer.h"
-#include "base/macros.h"
-#include "ui/display/display_observer.h"
-#include "ui/events/event_handler.h"
-#include "ui/gfx/geometry/point.h"
-
-namespace aura {
-class Window;
-}
-
-namespace ui {
-class LocatedEvent;
-}
-
-namespace ash {
-class ScreenshotDelegate;
-
-// This class controls a session of taking partial screenshot, i.e.: drawing
-// region rectangles during drag, and changing the mouse cursor to indicate
-// the current mode.
-// This class does not use aura::Window / views::Widget intentionally to avoid
-// the conflicts of window manager features like mouse captures or window focus.
-class ASH_EXPORT PartialScreenshotController : public ui::EventHandler,
-                                               public display::DisplayObserver {
- public:
-  PartialScreenshotController();
-  ~PartialScreenshotController() override;
-
-  // Starts the UI for taking partial screenshot; dragging to select a region.
-  // PartialScreenshotController manage their own lifetime so caller must not
-  // delete the returned values.
-  void StartPartialScreenshotSession(ScreenshotDelegate* screenshot_delegate);
-
- private:
-  friend class PartialScreenshotControllerTest;
-
-  class ScopedCursorSetter;
-  class PartialScreenshotLayer;
-
-  // Starts, ends, cancels, or updates the region selection.
-  void MaybeStart(const ui::LocatedEvent& event);
-  void Complete();
-  void Cancel();
-  void Update(const ui::LocatedEvent& event);
-
-  // ui::EventHandler:
-  void OnKeyEvent(ui::KeyEvent* event) override;
-  void OnMouseEvent(ui::MouseEvent* event) override;
-  void OnTouchEvent(ui::TouchEvent* event) override;
-
-  // display::DisplayObserver:
-  void OnDisplayAdded(const display::Display& new_display) override;
-  void OnDisplayRemoved(const display::Display& old_display) override;
-  void OnDisplayMetricsChanged(const display::Display& display,
-                               uint32_t changed_metrics) override;
-
-  // The data to build the screenshot region.
-  gfx::Point start_position_;
-  aura::Window* root_window_;
-
-  // Layers to create the visual effect of region selection.
-  std::map<aura::Window*, PartialScreenshotLayer*> layers_;
-
-  // The object to specify the crosshair cursor.
-  std::unique_ptr<ScopedCursorSetter> cursor_setter_;
-
-  // ScreenshotDelegate to take the actual screenshot. No ownership.
-  ScreenshotDelegate* screenshot_delegate_;
-
-  DISALLOW_COPY_AND_ASSIGN(PartialScreenshotController);
-};
-
-}  // namespace ash
-
-#endif  // #ifndef ASH_WM_PARTIAL_SCREENSHOT_VIEW_H_