Enable profile switching for standalone App Launcher via the Settings App.

chrome/browser/profiles/profile_manager.h

Index: chrome/browser/profiles/profile_manager.h
diff --git a/chrome/browser/profiles/profile_manager.h b/chrome/browser/profiles/profile_manager.h
index 9d1e03f7be98e6f2588722ed9ca352026de91515..3c47bb80d559e8a3522cc9c4f18d60538e9d10a9 100644
--- a/chrome/browser/profiles/profile_manager.h
+++ b/chrome/browser/profiles/profile_manager.h
@@ -101,6 +101,10 @@ class ProfileManager : public base::NonThreadSafe,
   // Same as instance method but provides the default user_data_dir as well.
   static Profile* GetLastUsedProfile();
 
+  // Get the path of the last used profile, or if that's undefined, the default
+  // profile.
+  FilePath GetLastUsedProfileDir(const FilePath& user_data_dir);
+
   // Get the Profiles which are currently open, i.e., have open browsers, or
   // were open the last time Chrome was running. The Profiles appear in the
   // order they were opened. The last used profile will be on the list, but its