Get drag and drop working on Win Ash.

ui/base/dragdrop/drag_utils_win.cc

 // 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.
 
 #include "ui/base/dragdrop/drag_utils.h"
 
 #include <objidl.h>
 #include <shlobj.h>
 #include <shobjidl.h>
 
@@ skipping 50 matching lines @@
   DCHECK(data_object && !size.IsEmpty());
   // InitializeFromBitmap() doesn't expect an alpha channel and is confused
   // by premultiplied colors, so unpremultiply the bitmap.
   // SetDragImageOnDataObject(HBITMAP) takes ownership of the bitmap.
   HBITMAP bitmap = CreateHBITMAPFromSkBitmap(
       SkBitmapOperations::UnPreMultiply(*image_skia.bitmap()));
 
   // Attach 'bitmap' to the data_object.
   SetDragImageOnDataObject(bitmap, size, cursor_offset,
       ui::OSExchangeDataProviderWin::GetIDataObject(*data_object));
+
+  // TODO: the above code is used in non-Ash, while below is used in Ash. If we
+  // could figure this context out then we wouldn't do unnecessary work. However
+  // as it stands getting this information in ui/base would be a layering
+  // violation.

[jam, 2013/01/04 22:23:02]

Basically this code block is doing thw ork for both non-ash and ash. I'm not
sure how to fix this given that this code is in ui/base/dragdrop. Other code in
ui/base depends on this (like ui/base/events/event.h) so moving it out of
ui/base doesn't seem to be an option.

I could easily plumb in the NativeView or NativeWindow associated with a drag
from all the callsites. But unless I can tell whether this is ash or not, then I
can't do only one part of this function. Really we don't even need to use
OSExchangeDataProviderWin on win ash at all; but again at the creation site
(which happens in ui/ sometimes) it would need to know ash vs non ash. The other
alternative is to plumb yet another delegate interface to chrome, although that
feels like having the layer know the same knowledge but wrapped differently.

wdyt?

+  data_object->provider().SetDragImage(image_skia, cursor_offset);
 }
 
 }  // namespace drag_utils