Make drag and drop work on webpage. Also slightly modify drag drop workflow.

chrome/browser/ui/views/tab_contents/native_tab_contents_view_aura.h

 // Copyright (c) 2011 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_VIEWS_TAB_CONTENTS_NATIVE_TAB_CONTENTS_VIEW_AURA_H_
 #define CHROME_BROWSER_UI_VIEWS_TAB_CONTENTS_NATIVE_TAB_CONTENTS_VIEW_AURA_H_
 #pragma once
 
 #include "chrome/browser/ui/views/tab_contents/native_tab_contents_view.h"
+#include "ui/base/events.h"
 #include "ui/views/widget/native_widget_aura.h"
 
+namespace aura {
+class DropTargetEvent;
+}
+
+namespace ui {
+class OSExchangeDataProviderAura;
+}
+
 class TabContents;
 
 class NativeTabContentsViewAura : public views::NativeWidgetAura,
                                   public NativeTabContentsView {
  public:
   explicit NativeTabContentsViewAura(
       internal::NativeTabContentsViewDelegate* delegate);
   virtual ~NativeTabContentsViewAura();
 
   TabContents* GetTabContents() const;
 
-  void EndDragging();
-
  private:
   // Overridden from NativeTabContentsView:
   virtual void InitNativeTabContentsView() OVERRIDE;
   virtual void Unparent() OVERRIDE;
   virtual RenderWidgetHostView* CreateRenderWidgetHostView(
       RenderWidgetHost* render_widget_host) OVERRIDE;
   virtual gfx::NativeWindow GetTopLevelNativeWindow() const OVERRIDE;
   virtual void SetPageTitle(const string16& title) OVERRIDE;
   virtual void StartDragging(const WebDropData& drop_data,
                              WebKit::WebDragOperationsMask ops,
                              const SkBitmap& image,
                              const gfx::Point& image_offset) OVERRIDE;
   virtual void CancelDrag() OVERRIDE;
   virtual bool IsDoingDrag() const OVERRIDE;
   virtual void SetDragCursor(WebKit::WebDragOperation operation) OVERRIDE;
   virtual views::NativeWidget* AsNativeWidget() OVERRIDE;
 
   // Overridden from views::NativeWidgetAura:
   virtual void OnBoundsChanged(const gfx::Rect& old_bounds,
                                const gfx::Rect& new_bounds) OVERRIDE;
   virtual bool OnMouseEvent(aura::MouseEvent* event) OVERRIDE;
+  virtual void OnDragEntered(const aura::DropTargetEvent& event) OVERRIDE;
+  virtual int OnDragUpdated(const aura::DropTargetEvent& event) OVERRIDE;
+  virtual void OnDragExited() OVERRIDE;
+  virtual int OnPerformDrop(const aura::DropTargetEvent& event) OVERRIDE;
+
+  // Informs the renderer that the drag operation it initiated has ended and
+  // |ops| drag operations were applied.
+  void EndDrag(WebKit::WebDragOperationsMask ops);
 
   internal::NativeTabContentsViewDelegate* delegate_;
 
+  WebKit::WebDragOperationsMask current_drag_op_;
+
   DISALLOW_COPY_AND_ASSIGN(NativeTabContentsViewAura);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_TAB_CONTENTS_NATIVE_TAB_CONTENTS_VIEW_AURA_H_