[Mac] Adjust omnibox decoration dragging to keep image under mouse.

chrome/browser/cocoa/location_bar/location_bar_decoration.h

Index: chrome/browser/cocoa/location_bar/location_bar_decoration.h
diff --git a/chrome/browser/cocoa/location_bar/location_bar_decoration.h b/chrome/browser/cocoa/location_bar/location_bar_decoration.h
index 51571cceae85d63e48a96e4c8d989e12708833d1..56a4b83bcf7afa895e06b246fba3ec2e19f0f825 100644
--- a/chrome/browser/cocoa/location_bar/location_bar_decoration.h
+++ b/chrome/browser/cocoa/location_bar/location_bar_decoration.h
@@ -59,6 +59,12 @@ class LocationBarDecoration {
   // The image to drag.
   virtual NSImage* GetDragImage() { return nil; }
 
+  // Return the place within the decoration's frame where the
+  // |GetDragImage()| comes from.  This is used to make sure the image
+  // appears correctly under the mouse while dragging.  |frame|
+  // matches the frame passed to |DrawInFrame()|.
+  virtual NSRect GetDragImageFrame(NSRect frame) { return NSZeroRect; }
+
   // The pasteboard to drag.
   virtual NSPasteboard* GetDragPasteboard() { return nil; }