Refactor intra-strip panel drags by introducing PanelDragController.

chrome/browser/ui/panels/panel_drag_controller.h

+// 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 CHROME_BROWSER_UI_PANELS_PANEL_DRAG_CONTROLLER_H_
+#define CHROME_BROWSER_UI_PANELS_PANEL_DRAG_CONTROLLER_H_
+#pragma once
+
+#include <set>
+#include "base/basictypes.h"
+#include "ui/gfx/point.h"
+
+class Panel;
+
+// Responsible for handling drags initiated for all panel strips, including

[jennb, 2012/02/17 21:28:45]

s/panel strips/panels  ?

[jianli, 2012/02/17 23:52:56]

Done.

+// both intra-strip and inter-strip drags.
+class PanelDragController {
+ public:
+  PanelDragController();
+  ~PanelDragController();
+
+  void StartDragging(Panel* panel);
+  void Drag(int delta_x, int delta_y);
+  void EndDragging(bool cancelled);
+
+  // Checks if |panel| can be removed now. If not, it will be scheduled to be
+  // removed later.
+  bool CanRemovePanel(Panel* panel);
+
+  Panel* dragging_panel() const { return dragging_panel_; }
+
+ private:
+  void DelayedRemove();
+
+  // Panel currently being dragged.
+  Panel* dragging_panel_;
+
+  // Stores the panels that are pending to remove. We want to delay the removal
+  // when we're in the process of the dragging.
+  std::set<Panel*> panels_pending_to_remove_;
+
+  DISALLOW_COPY_AND_ASSIGN(PanelDragController);
+};
+
+#endif  // CHROME_BROWSER_UI_PANELS_PANEL_DRAG_CONTROLLER_H_