Do not use assets for Ash window control button backgrounds

ash/frame/custom_frame_view_ash_unittest.cc

Index: ash/frame/custom_frame_view_ash_unittest.cc
diff --git a/ash/frame/custom_frame_view_ash_unittest.cc b/ash/frame/custom_frame_view_ash_unittest.cc
index ab3656eb904ad16ea526be3501b466ec64542746..bc7df55cfac52fd9e3b7bb2e0a1f1e145b244128 100644
--- a/ash/frame/custom_frame_view_ash_unittest.cc
+++ b/ash/frame/custom_frame_view_ash_unittest.cc
@@ -128,14 +128,9 @@ TEST_F(CustomFrameViewAshTest, HeaderHeight) {
   scoped_ptr<views::Widget> widget(CreateWidget(delegate));
   widget->Show();
 
-  ui::ResourceBundle& rb = ui::ResourceBundle::GetSharedInstance();
-  gfx::ImageSkia* close_button =
-      rb.GetImageSkiaNamed(IDR_AURA_WINDOW_CONTROL_BACKGROUND_H);
-
   // The header should have enough room for the window controls. The
   // header/content separator line overlays the window controls.
-  EXPECT_EQ(close_button->height(),
-            delegate->custom_frame_view()->GetHeaderView()->height());
+  EXPECT_EQ(33, delegate->custom_frame_view()->GetHeaderView()->height());
 }
 
 // Verify that CustomFrameViewAsh returns the correct minimum and maximum frame