mash: remove more shell/shelf WmWindow usage.

ash/wm/window_cycle_controller_unittest.cc

Index: ash/wm/window_cycle_controller_unittest.cc
diff --git a/ash/wm/window_cycle_controller_unittest.cc b/ash/wm/window_cycle_controller_unittest.cc
index d195954014c8b88e09a210ea8228fff87a1769a7..814636646634aa2d5d69938189e0dcff8aa20752 100644
--- a/ash/wm/window_cycle_controller_unittest.cc
+++ b/ash/wm/window_cycle_controller_unittest.cc
@@ -409,8 +409,7 @@ TEST_F(WindowCycleControllerTest, AlwaysOnTopMultipleRootWindows) {
   EXPECT_EQ(root_windows[0], window1->GetRootWindow());
 
   // Move the active root window to the secondary root and create two windows.
-  ScopedRootWindowForNewWindows root_for_new_windows(
-      WmWindow::Get(root_windows[1]));
+  ScopedRootWindowForNewWindows root_for_new_windows(root_windows[1]);
   std::unique_ptr<Window> window2(CreateTestWindowInShellWithId(2));
   EXPECT_EQ(root_windows[1], window2->GetRootWindow());