Enable touch-initiated drag-drop work on Windows

content/browser/web_contents/web_drag_source_win.h

Index: content/browser/web_contents/web_drag_source_win.h
diff --git a/content/browser/web_contents/web_drag_source_win.h b/content/browser/web_contents/web_drag_source_win.h
index 898f3c3ada546fd21966d763e5dd9d0993247d63..abf65b4a669996997a775ab500c37dd1e30f091c 100644
--- a/content/browser/web_contents/web_drag_source_win.h
+++ b/content/browser/web_contents/web_drag_source_win.h
@@ -39,6 +39,7 @@ class WebDragSource : public ui::DragSourceWin,
   virtual void OnDragSourceCancel();
   virtual void OnDragSourceDrop();
   virtual void OnDragSourceMove();
+  virtual bool ShouldDropDragSource(BOOL escape_pressed, DWORD key_state);
 
  private:
   // Cannot construct thusly.
@@ -48,6 +49,8 @@ class WebDragSource : public ui::DragSourceWin,
   // by posting a task to this function.
   void DelayedOnDragSourceDrop();
 
+  void OnDragSourceEnded();
+
   // Keep a reference to the window so we can translate the cursor position.
   gfx::NativeWindow source_wnd_;