Remove workaround for bug 748219, which seems to have been fixed in the meantime.

layout/base/nsDisplayList.cpp

@@ -3019,11 +3019,6 @@ nsDisplayThemedBackground::GetBoundsInternal() {
   presContext->GetTheme()->
       GetWidgetOverflow(presContext->DeviceContext(), mFrame,
                         mFrame->StyleDisplay()->mAppearance, &r);
-#ifdef XP_MACOSX
-  // Bug 748219
-  r.Inflate(mFrame->PresContext()->AppUnitsPerDevPixel());
-#endif
-
   return r + ToReferenceFrame();
 }