Delete ash-based code for Windows drag-and-drop graphics.

ui/base/dragdrop/os_exchange_data_provider_mac.mm

Index: ui/base/dragdrop/os_exchange_data_provider_mac.mm
diff --git a/ui/base/dragdrop/os_exchange_data_provider_mac.mm b/ui/base/dragdrop/os_exchange_data_provider_mac.mm
index 11b0a495bb12312609aef9ad8992d20b8ca1724c..2014408c9fbf7fe1d65a8e0ea1404cac3f9d69be 100644
--- a/ui/base/dragdrop/os_exchange_data_provider_mac.mm
+++ b/ui/base/dragdrop/os_exchange_data_provider_mac.mm
@@ -181,11 +181,11 @@ void OSExchangeDataProviderMac::SetDragImage(
   cursor_offset_ = cursor_offset;
 }
 
-const gfx::ImageSkia& OSExchangeDataProviderMac::GetDragImage() const {
+gfx::ImageSkia OSExchangeDataProviderMac::GetDragImage() const {
   return drag_image_;
 }
 
-const gfx::Vector2d& OSExchangeDataProviderMac::GetDragImageOffset() const {
+gfx::Vector2d OSExchangeDataProviderMac::GetDragImageOffset() const {
   return cursor_offset_;
 }