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

ash/frame/caption_buttons/frame_size_button_unittest.cc

Index: ash/frame/caption_buttons/frame_size_button_unittest.cc
diff --git a/ash/frame/caption_buttons/frame_size_button_unittest.cc b/ash/frame/caption_buttons/frame_size_button_unittest.cc
index a14c83d6da14d35051d397deb27a184bfaa6d856..53f53c15edc42930c26b774530ab31a224d08e38 100644
--- a/ash/frame/caption_buttons/frame_size_button_unittest.cc
+++ b/ash/frame/caption_buttons/frame_size_button_unittest.cc
@@ -331,7 +331,7 @@ TEST_F(FrameSizeButtonTest, ResetButtonsAfterClick) {
   EXPECT_EQ(CAPTION_BUTTON_ICON_LEFT_SNAPPED, minimize_button()->icon());
   EXPECT_EQ(CAPTION_BUTTON_ICON_RIGHT_SNAPPED, close_button()->icon());
 
-  const gfx::Rect& kWorkAreaBoundsInScreen =
+  const gfx::Rect kWorkAreaBoundsInScreen =

[sky, 2017/01/18 23:33:45]

Generally k is reserved for values that are the same through the life time of
the program. While that is likely true here because this function is only called
one the naming here isn't typical, please change to work_area_bounds_in_screen.

[krasin1, 2017/01/19 17:36:38]

Done.

       display::Screen::GetScreen()->GetPrimaryDisplay().work_area();
   generator.MoveMouseTo(kWorkAreaBoundsInScreen.bottom_left());
 
@@ -382,7 +382,7 @@ TEST_F(FrameSizeButtonTest, SizeButtonPressedWhenSnapButtonHovered) {
   // Moving the mouse far away from the caption buttons and then moving it over
   // the close button (snap right button) should hover the close button and
   // keep the size button pressed.
-  const gfx::Rect& kWorkAreaBoundsInScreen =
+  const gfx::Rect kWorkAreaBoundsInScreen =
       display::Screen::GetScreen()->GetPrimaryDisplay().work_area();
   generator.MoveMouseTo(kWorkAreaBoundsInScreen.bottom_left());
   EXPECT_TRUE(AllButtonsInNormalState());