ash: fix multiple stack-use-after-scope issues with GetPrimaryDisplay use.

ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc

Index: ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc
diff --git a/ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc b/ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc
index d40daa8d8adcc3d512d3c2aa7dc6f42a198f1c60..3ae5f22fde3c39a6cd00b69b545b562591324af0 100644
--- a/ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc
+++ b/ash/system/web_notification/ash_popup_alignment_delegate_unittest.cc
@@ -71,7 +71,7 @@ class AshPopupAlignmentDelegateTest : public test::AshTestBase {
   }
 
   Position GetPositionInDisplay(const gfx::Point& point) {
-    const gfx::Rect& work_area =
+    const gfx::Rect work_area =
         display::Screen::GetScreen()->GetPrimaryDisplay().work_area();
     const gfx::Point center_point = work_area.CenterPoint();
     if (work_area.x() > point.x() || work_area.y() > point.y() ||