Enable ash window cycle UI by default.

ash/accelerators/accelerator_controller_unittest.cc

Index: ash/accelerators/accelerator_controller_unittest.cc
diff --git a/ash/accelerators/accelerator_controller_unittest.cc b/ash/accelerators/accelerator_controller_unittest.cc
index 58b8e5887a5cb230895860bed2bf1100732a62bb..a522f01f7790dd94e2c0d505a08e0e6f086ab34f 100644
--- a/ash/accelerators/accelerator_controller_unittest.cc
+++ b/ash/accelerators/accelerator_controller_unittest.cc
@@ -1124,9 +1124,15 @@ TEST_F(PreferredReservedAcceleratorsTest, AcceleratorsWithFullscreen) {
   EXPECT_TRUE(test_api.is_animating_lock());
 #endif
 
+  auto press_alt_tab = [&generator]() {
+    generator.PressKey(ui::VKEY_TAB, ui::EF_ALT_DOWN);
+    // Release the alt key to complete Alt+Tab.
+    generator.ReleaseKey(ui::VKEY_MENU, ui::EF_NONE);
+  };
+
   // A fullscreen window can consume ALT-TAB (preferred).
   ASSERT_EQ(w1, wm::GetActiveWindow());
-  generator.PressKey(ui::VKEY_TAB, ui::EF_ALT_DOWN);
+  press_alt_tab();
   ASSERT_EQ(w1, wm::GetActiveWindow());
   ASSERT_NE(w2, wm::GetActiveWindow());
 
@@ -1141,7 +1147,7 @@ TEST_F(PreferredReservedAcceleratorsTest, AcceleratorsWithFullscreen) {
   ASSERT_FALSE(w1_state->IsFullscreen());
 
   EXPECT_EQ(w1, wm::GetActiveWindow());
-  generator.PressKey(ui::VKEY_TAB, ui::EF_ALT_DOWN);

[Evan Stade, 2016/08/12 22:51:57]

before, alt+tab was enough for activation, now you must release alt. This is
also a handy way to test that alt+tab/release works even before the UI's show
delay is finished.

+  press_alt_tab();
   ASSERT_NE(w1, wm::GetActiveWindow());
   ASSERT_EQ(w2, wm::GetActiveWindow());
 }