Allow closing root window, or pressing the power button to shutdown ash_shell, and chrome /w chrome…

ash/wm/power_button_controller.cc

Index: ash/wm/power_button_controller.cc
diff --git a/ash/wm/power_button_controller.cc b/ash/wm/power_button_controller.cc
index 73c1a3bbbafbd8155db17c41bbf708ec6b40763b..55d59931ee8f75ef047a408b53b320f0f9914044 100644
--- a/ash/wm/power_button_controller.cc
+++ b/ash/wm/power_button_controller.cc
@@ -6,6 +6,7 @@
 
 #include "ash/ash_switches.h"
 #include "ash/shell.h"
+#include "ash/shell_delegate.h"
 #include "ash/shell_window_ids.h"
 #include "ash/wm/cursor_manager.h"
 #include "base/command_line.h"
@@ -472,6 +473,12 @@ void PowerButtonController::OnRootWindowResized(const aura::RootWindow* root,
     background_layer_->SetBounds(gfx::Rect(root->bounds().size()));
 }
 
+void PowerButtonController::OnRootWindowHostCloseRequested(
+                                                const aura::RootWindow*) {
+  if(Shell::GetInstance() && Shell::GetInstance()->delegate())
+    Shell::GetInstance()->delegate()->Exit();
+}
+
 bool PowerButtonController::LoggedInAsNonGuest() const {
   if (login_status_ == user::LOGGED_IN_NONE)
     return false;