chromeos: Move device shutdown handling out of chrome into ash

ash/BUILD.gn

Index: ash/BUILD.gn
diff --git a/ash/BUILD.gn b/ash/BUILD.gn
index 41ab1777e7fefcad799d393733b02008162cd7b3..d2551a86c0eaca53ee435cf32d14c6b3eb0edb1e 100644
--- a/ash/BUILD.gn
+++ b/ash/BUILD.gn
@@ -187,6 +187,8 @@ component("ash") {
     "common/shelf/wm_shelf_util.cc",
     "common/shelf/wm_shelf_util.h",
     "common/shell_delegate.h",
+    "common/shutdown_controller.cc",
+    "common/shutdown_controller.h",
     "common/system/accessibility_observer.h",
     "common/system/brightness_control_delegate.h",
     "common/system/chromeos/audio/audio_detailed_view.cc",
@@ -308,7 +310,6 @@ component("ash") {
     "common/system/chromeos/session/tray_session_length_limit.h",
     "common/system/chromeos/settings/tray_settings.cc",
     "common/system/chromeos/settings/tray_settings.h",
-    "common/system/chromeos/shutdown_policy_observer.h",
     "common/system/chromeos/supervised/custodian_info_tray_observer.h",
     "common/system/chromeos/supervised/tray_supervised_user.cc",
     "common/system/chromeos/supervised/tray_supervised_user.h",
@@ -811,8 +812,6 @@ component("ash") {
     "wm/session_state_animator.h",
     "wm/session_state_animator_impl.cc",
     "wm/session_state_animator_impl.h",
-    "wm/shutdown_client_proxy.cc",
-    "wm/shutdown_client_proxy.h",
     "wm/stacking_controller.cc",
     "wm/stacking_controller.h",
     "wm/system_gesture_event_filter.cc",