[CrOS] Initial rough cut of alt-tab window cycling UI.

ash/common/ash_switches.cc

Index: ash/common/ash_switches.cc
diff --git a/ash/common/ash_switches.cc b/ash/common/ash_switches.cc
index ef0fb1c7a068a4466092cb342813c646906fc0c1..b0359e8f1607af331e797ba67bb4034af5f789da 100644
--- a/ash/common/ash_switches.cc
+++ b/ash/common/ash_switches.cc
@@ -75,6 +75,9 @@ const char kAshEnableSoftwareMirroring[] = "ash-enable-software-mirroring";
 // flag is removed.
 const char kAshEnableTouchViewTesting[] = "ash-enable-touch-view-testing";
 
+// Enables the window cycling UI (more visual feedback for alt-tab).
+const char kAshEnableWindowCycleUi[] = "ash-enable-window-cycle-ui";
+
 // When this flag is set, system sounds will not be played.
 const char kAshDisableSystemSounds[] = "ash-disable-system-sounds";