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..9658acd3626bfa469545cc73ecd0b9108cd9bf3f 100644
--- a/ash/mus/bridge/wm_shell_mus.cc
+++ b/ash/mus/bridge/wm_shell_mus.cc
@@ -32,6 +32,7 @@
 #include "ash/shared/immersive_fullscreen_controller.h"
 #include "ash/shell.h"
 #include "ash/shell_init_params.h"
+#include "ash/wm/lock_state_controller.h"
 #include "ash/wm/window_util.h"
 #include "base/memory/ptr_util.h"
 #include "components/user_manager/user_info_impl.h"
@@ -63,7 +64,11 @@ 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 {
@@ -390,7 +395,7 @@ void WmShellMus::RemovePointerWatcher(views::PointerWatcher* watcher) {
 }
 
 void WmShellMus::RequestShutdown() {
-  NOTIMPLEMENTED();
+  Shell::GetInstance()->lock_state_controller()->RequestShutdown();

[James Cook, 2017/01/25 01:02:59]

It looks like this is the same implementation as WmShellAura. Can the
implementation move into the base class WmShell, or better yet move back into
ash::Shell?

[Daniel Erat, 2017/01/25 01:10:51]

good suggestion. i think that this method is only called from
ash/common/system/date/date_default_view.cc and
ash/common/system/tiles/tiles_default_view.cc, but both of those files seem very
dependent on WmShell (and don't depend on ash::Shell at all).

would you prefer that i update them to instead call
ash::Shell::GetInstance()->lock_state_controller()->RequestShutdown(), or that i
move this RequestShutdown method to WmShell? in other words, are we all-in on
using the ash::Shell singleton now?

[James Cook, 2017/01/25 01:17:38]

I think we're OK using ash::Shell::GetInstance() now, and I think we should try
to keep things that are the same in classic ash and mash in ash::Shell.

(Those system files date to the time when ash::Shell was disallowed.)

[Daniel Erat, 2017/01/25 01:40:19]

ah, i see that there's a relevant todo in ash/common/wm_shell.h:

  // Displays the shutdown animation and requests a system shutdown or system
  // restart depending on the the state of the |RebootOnShutdown| device policy.
  // TODO(mash): Remove this method and call LockStateController directly when
  // it is available to code in ash/common.
  virtual void RequestShutdown() = 0;

LockStateController is in ash/wm, so i think that code under ash/common can't
depend on it. moving LSC to ash/common may not be straightforward: it depends on
ash/wm/session_state_animator.h, which depends on ash/wm/window_animations.h,
etc.

should i just move the RequestShutdown() method to ash::Shell for now?

[James Cook, 2017/01/25 01:45:23]

I wouldn't move LSC to ash/common - I think this comment is slightly out of
date.

I think code in ash/common can in general use code in ash/wm now. (I mean, LSC
is being used in classic ash and with this CL we're going to use it mash also,
so there's no point to a deps ban. The deps in ash/common/DEPS originally had
-ash but don't anymore. I'm not sure why sky didn't remove all the other +ash
references.)  Does checkdeps complain?

If the DEPS end up getting in the way I'm OK with putting it in ash::Shell.

[Daniel Erat, 2017/01/25 02:06:10]

thanks, i've made this change and am testing the DEPS now (via a cq dry run,
because i'm not quite sure how to run checkdeps.py locally...).

 }
 
 bool WmShellMus::IsTouchDown() {