mash: Migrate tray IME view to wm common types, move to //ash/common

ash/mus/bridge/wm_shell_mus.cc

Index: ash/mus/bridge/wm_shell_mus.cc
diff --git a/ash/mus/bridge/wm_shell_mus.cc b/ash/mus/bridge/wm_shell_mus.cc
index d21336b84eac59255eda2890f2c96d4d1372c555..035fde264e596553f2aee017228c350134b4df7f 100644
--- a/ash/mus/bridge/wm_shell_mus.cc
+++ b/ash/mus/bridge/wm_shell_mus.cc
@@ -305,5 +305,11 @@ void WmShellMus::OnWillDestroyClient(::mus::WindowTreeClient* client) {
   RemoveClientObserver();
 }
 
+#if defined(OS_CHROMEOS)
+void WmShellMus::ToggleIgnoreExternalKeyboard() {
+  NOTIMPLEMENTED();
+}
+#endif  // defined(OS_CHROMEOS)
+
 }  // namespace mus
 }  // namespace ash