arc: Use incognito profile for OptIn and cookie fetcher

chrome/browser/chromeos/arc/arc_auth_ui.h

Index: chrome/browser/chromeos/arc/arc_auth_ui.h
diff --git a/chrome/browser/chromeos/arc/arc_auth_ui.h b/chrome/browser/chromeos/arc/arc_auth_ui.h
index 7e810dc676a296d7e345f2900b2f93db13926db3..eb47b495277d13f5b1eb04493fa575fa116a78f7 100644
--- a/chrome/browser/chromeos/arc/arc_auth_ui.h
+++ b/chrome/browser/chromeos/arc/arc_auth_ui.h
@@ -25,6 +25,8 @@ class ArcAuthUI : public ui::WebDialogDelegate,
  public:
   class Delegate {
    public:
+    // Called when AuthCode was fetched.
+    virtual void OnAuthCodeFetchedFromUI(const std::string& auth_code) = 0;
     // Called when dialog is closed.
     virtual void OnAuthUIClosed() = 0;