mash: Convert FocusCycler to wm common types and move to //ash/common

ash/common/wm_shell.h

Index: ash/common/wm_shell.h
diff --git a/ash/common/wm_shell.h b/ash/common/wm_shell.h
index be70d71e221621fe6da9d565eb187775883c9a68..fbc418a0c3400060e2d8a9d6aff6eed3d4c80156 100644
--- a/ash/common/wm_shell.h
+++ b/ash/common/wm_shell.h
@@ -20,6 +20,7 @@ class Rect;
 namespace ash {
 
 class AccessibilityDelegate;
+class FocusCycler;
 class MruWindowTracker;
 class SessionStateDelegate;
 class ShellObserver;
@@ -43,6 +44,8 @@ class ASH_EXPORT WmShell {
   static WmShell* Get();
   static bool HasInstance() { return instance_ != nullptr; }
 
+  FocusCycler* focus_cycler() { return focus_cycler_.get(); }
+
   WmSystemTrayNotifier* system_tray_notifier() {
     return system_tray_notifier_.get();
   }
@@ -140,6 +143,7 @@ class ASH_EXPORT WmShell {
 
   static WmShell* instance_;
 
+  std::unique_ptr<FocusCycler> focus_cycler_;
   std::unique_ptr<WmSystemTrayNotifier> system_tray_notifier_;
   std::unique_ptr<SystemTrayDelegate> system_tray_delegate_;
 };