mash: Make the power button shut the system down.

ash/wm/lock_state_controller.cc

Index: ash/wm/lock_state_controller.cc
diff --git a/ash/wm/lock_state_controller.cc b/ash/wm/lock_state_controller.cc
index 31a874d1583cc4d34e7b6034f799abb46c97b8ec..4aef37f54f392151621975a8b3087e00d8bf1fd1 100644
--- a/ash/wm/lock_state_controller.cc
+++ b/ash/wm/lock_state_controller.cc
@@ -162,8 +162,10 @@ void LockStateController::RequestShutdown() {
   shutting_down_ = true;
 
   Shell* shell = Shell::GetInstance();
-  shell->cursor_manager()->HideCursor();
-  shell->cursor_manager()->LockCursor();
+  if (shell->cursor_manager()) {
+    shell->cursor_manager()->HideCursor();
+    shell->cursor_manager()->LockCursor();
+  }
 
   animator_->StartAnimation(
       SessionStateAnimator::ROOT_CONTAINER,
@@ -200,8 +202,10 @@ void LockStateController::OnAppTerminating() {
   if (!shutting_down_) {
     shutting_down_ = true;
     Shell* shell = Shell::GetInstance();
-    shell->cursor_manager()->HideCursor();
-    shell->cursor_manager()->LockCursor();
+    if (shell->cursor_manager()) {
+      shell->cursor_manager()->HideCursor();
+      shell->cursor_manager()->LockCursor();
+    }
     animator_->StartAnimation(SessionStateAnimator::kAllNonRootContainersMask,
                               SessionStateAnimator::ANIMATION_HIDE_IMMEDIATELY,
                               SessionStateAnimator::ANIMATION_SPEED_IMMEDIATE);
@@ -271,7 +275,8 @@ void LockStateController::OnPreShutdownAnimationTimeout() {
   shutting_down_ = true;
 
   Shell* shell = Shell::GetInstance();
-  shell->cursor_manager()->HideCursor();
+  if (shell->cursor_manager())
+    shell->cursor_manager()->HideCursor();
 
   StartRealShutdownTimer(false);
 }
@@ -307,7 +312,8 @@ void LockStateController::OnRealPowerTimeout() {
 void LockStateController::StartCancellableShutdownAnimation() {
   Shell* shell = Shell::GetInstance();
   // Hide cursor, but let it reappear if the mouse moves.
-  shell->cursor_manager()->HideCursor();
+  if (shell->cursor_manager())
+    shell->cursor_manager()->HideCursor();
 
   animator_->StartAnimation(
       SessionStateAnimator::ROOT_CONTAINER,