Support Drag and Drop across displays.

ash/drag_drop/drag_image_view.cc

Index: ash/drag_drop/drag_image_view.cc
diff --git a/ash/drag_drop/drag_image_view.cc b/ash/drag_drop/drag_image_view.cc
index 7a138f3ed0424f7ab5aa827c83d98a90b2f5eecf..b6a32f83c69497215f0ef2acf5a27451678c537a 100644
--- a/ash/drag_drop/drag_image_view.cc
+++ b/ash/drag_drop/drag_image_view.cc
@@ -5,6 +5,7 @@
 #include "ash/drag_drop/drag_image_view.h"
 
 #include "ash/wm/shadow_types.h"
+#include "ui/aura/window.h"
 #include "ui/views/widget/widget.h"
 
 namespace ash {
@@ -23,6 +24,7 @@ Widget* CreateDragWidget() {
   params.transparent = true;
   drag_widget->Init(params);
   drag_widget->SetOpacity(0xFF);
+  drag_widget->GetNativeWindow()->set_owned_by_parent(false);

[mazda, 2012/08/24 08:29:01]

This is needed to make the aura window not deleted by RootWindow dtor.
The aura window of this widget is added to DragImageAndTooltipContainer and is
not moved to primary window when the secondary display is disconnected (see
RootWindowController::ReparentAllWindows).

   SetShadowType(drag_widget->GetNativeView(), SHADOW_TYPE_NONE);
   return drag_widget;
 }