Support Drag and Drop across displays.

ash/drag_drop/drag_drop_tracker.h

Index: ash/drag_drop/drag_drop_tracker.h
diff --git a/ash/drag_drop/drag_drop_tracker.h b/ash/drag_drop/drag_drop_tracker.h
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+// Copyright (c) 2012 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_DRAG_DROP_DRAG_DROP_TRACKER_H_
+#define ASH_DRAG_DROP_DRAG_DROP_TRACKER_H_
+
+#include "ash/ash_export.h"
+#include "base/basictypes.h"
+#include "ui/base/event.h"
+
+namespace aura {
+class RootWindow;
+class Window;
+}
+
+namespace ash {
+namespace internal {
+
+class ASH_EXPORT DragDropTracker {
+ public:
+  DragDropTracker();
+  ~DragDropTracker();
+
+  // Starts tracking the drag events sent to |root_window|.
+  void StartTracking(aura::RootWindow* root_window);
+
+  // Stop tracking drag events.
+  void StopTracking();
+
+  // Gets the target located at |event| in the coordinates of the root window
+  // given to StartTracking.
+  aura::Window* GetTarget(const ui::LocatedEvent& event);
+
+  // Converts the locations of |event| in the coordinates of the root window
+  // given to StartTracking to the ones in |target|'s coordinates.
+  // Caller takes ownership of the returned object.
+  ui::MouseEvent* ConvertMouseEvent(aura::Window* target,
+                                    const ui::MouseEvent& event);
+
+ private:
+  // A window for capturing drag events while dragging.
+  aura::Window* capture_window_;
+
+  DISALLOW_COPY_AND_ASSIGN(DragDropTracker);
+};
+
+}  // namespace internal
+}  // namespace ash
+
+#endif  // ASH_DRAG_DROP_DRAG_DROP_TRACKER_H_