chromeos: Move device shutdown handling out of chrome into ash

ash/common/system/tiles/tray_tiles.cc

Index: ash/common/system/tiles/tray_tiles.cc
diff --git a/ash/common/system/tiles/tray_tiles.cc b/ash/common/system/tiles/tray_tiles.cc
index 9c68db2f3c6e7919531abb44edf2210b271dcbbb..227a4c9fb710b3fe6bf265139e2f1219af630426 100644
--- a/ash/common/system/tiles/tray_tiles.cc
+++ b/ash/common/system/tiles/tray_tiles.cc
@@ -22,6 +22,10 @@ views::View* TrayTiles::GetHelpButtonView() const {
   return default_view_->GetHelpButtonView();
 }
 
+TilesDefaultView* TrayTiles::GetDefaultViewForTesting() const {
+  return default_view_;
+}
+
 views::View* TrayTiles::CreateDefaultViewForTesting(LoginStatus status) {
   return CreateDefaultView(status);
 }