Show an InfoBar when trying to start Packaged Apps from Metro mode.

apps/pref_names.cc

Index: apps/pref_names.cc
diff --git a/apps/pref_names.cc b/apps/pref_names.cc
index 15a33f936a52114979718cba639d60bbcb1db634..762ce7ddd06f8a20650a135392d00ecbdd444314 100644
--- a/apps/pref_names.cc
+++ b/apps/pref_names.cc
@@ -12,6 +12,10 @@ namespace prefs {
 const char kAppLauncherIsEnabled[] =
     "apps.app_launcher.should_show_apps_page";
 
+// If set, the user requested to launch the app with this extension id while
+// in Metro mode, and then relaunched to Desktop mode to start it.
+const char kRestartFromMetroWithAppLaunch[] = "apps.start_app_on_relaunch";
+
 }  // namespace prefs
 
 }  // namespace apps