mash: Make the power button shut the system down.

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 ca58c14203786330215a5d4f1997ae352226815f..b45d518ed3e41d6af39b2669b118098ba48b38b8 100644
--- a/ash/mus/bridge/wm_shell_mus.cc
+++ b/ash/mus/bridge/wm_shell_mus.cc
@@ -63,7 +63,11 @@ class SessionStateDelegateStub : public SessionStateDelegate {
   int GetMaximumNumberOfLoggedInUsers() const override { return 3; }
   int NumberOfLoggedInUsers() const override { return 1; }
   bool IsActiveUserSessionStarted() const override { return true; }
-  bool CanLockScreen() const override { return true; }
+  bool CanLockScreen() const override {
+    // The Chrome OS session_manager process currently rejects screen-lock
+    // requests due to no user being logged in.
+    return false;
+  }
   bool IsScreenLocked() const override { return screen_locked_; }
   bool ShouldLockScreenAutomatically() const override { return false; }
   void LockScreen() override {
@@ -389,10 +393,6 @@ void WmShellMus::RemovePointerWatcher(views::PointerWatcher* watcher) {
   pointer_watcher_event_router_->RemovePointerWatcher(watcher);
 }
 
-void WmShellMus::RequestShutdown() {
-  NOTIMPLEMENTED();
-}
-
 bool WmShellMus::IsTouchDown() {
   // TODO: implement me, http://crbug.com/634967.
   // NOTIMPLEMENTED is too spammy here.