arc: Use incognito profile for OptIn and cookie fetcher

chrome/browser/chromeos/arc/arc_auth_ui.cc

Index: chrome/browser/chromeos/arc/arc_auth_ui.cc
diff --git a/chrome/browser/chromeos/arc/arc_auth_ui.cc b/chrome/browser/chromeos/arc/arc_auth_ui.cc
index 6bbd157defe3b02f7ea4d29028523724fa4fcf31..8a9b639ce1b6ae758d765b65f877910eb2c2dfce 100644
--- a/chrome/browser/chromeos/arc/arc_auth_ui.cc
+++ b/chrome/browser/chromeos/arc/arc_auth_ui.cc
@@ -98,7 +98,7 @@ void ArcAuthUI::OnLoadingStateChanged(content::WebContents* source) {
 }
 
 void ArcAuthUI::OnAuthCodeFetched(const std::string& auth_code) {
-  ArcAuthService::Get()->SetAuthCodeAndStartArc(auth_code);
+  delegate_->OnAuthCodeFetchedFromUI(auth_code);
 }
 
 void ArcAuthUI::OnAuthCodeNeedUI() {}