gtk: Split CustomDrag into multiple pieces.

chrome/browser/ui/gtk/download/download_item_drag.h

+// Copyright 2013 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_GTK_DOWNLOAD_DOWNLOAD_ITEM_DRAG_H_
+#define CHROME_BROWSER_UI_GTK_DOWNLOAD_DOWNLOAD_ITEM_DRAG_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/ui/gtk/custom_drag.h"
+
+namespace content {
+class DownloadItem;
+}
+
+// Encapsulates functionality for drags of download items.
+class DownloadItemDrag : public CustomDrag {
+ public:
+  // Sets |widget| as a source for drags pertaining to |item|. No
+  // DownloadItemDrag object is created.
+  // It is safe to call this multiple times with different values of |icon|.
+  static void SetSource(GtkWidget* widget,
+                        const content::DownloadItem* item,
+                        gfx::Image* icon);
+
+  // Creates a new DownloadItemDrag, the lifetime of which is tied to the
+  // system drag.
+  static void BeginDrag(const content::DownloadItem* item, gfx::Image* icon);
+
+ private:
+  class DragData;
+
+  DownloadItemDrag(const content::DownloadItem* item, gfx::Image* icon);
+  virtual ~DownloadItemDrag();
+
+  virtual void OnDragDataGet(GtkWidget* widget,
+                             GdkDragContext* context,
+                             GtkSelectionData* selection_data,
+                             guint target_type,
+                             guint time) OVERRIDE;
+
+  scoped_ptr<DragData> drag_data_;
+
+  DISALLOW_COPY_AND_ASSIGN(DownloadItemDrag);
+};
+
+
+#endif  // CHROME_BROWSER_UI_GTK_DOWNLOAD_DOWNLOAD_ITEM_DRAG_H_