Make sure auth error reporting handles guest mode correctly.

chrome/browser/profiles/profiles_state.h

Index: chrome/browser/profiles/profiles_state.h
diff --git a/chrome/browser/profiles/profiles_state.h b/chrome/browser/profiles/profiles_state.h
index 005cf363bcf8c46201c19c08cea8e60213df21cd..788366f6f57e803bd32d79468fd289a6bf6aa405 100644
--- a/chrome/browser/profiles/profiles_state.h
+++ b/chrome/browser/profiles/profiles_state.h
@@ -11,6 +11,7 @@
 class Browser;
 class PrefRegistrySimple;
 class Profile;
+class SigninErrorController;
 namespace base { class FilePath; }
 
 namespace profiles {
@@ -52,6 +53,11 @@ bool IsRegularOrGuestSession(Browser* browser);
 // version of the Gaia profile picture.
 void UpdateGaiaProfilePhotoIfNeeded(Profile* profile);
 
+// Returns the sign-in error controller for the given profile.  Some profiles,
+// like guest profiles, may not have a controller so this function may return
+// NULL.
+SigninErrorController* GetSigninErrorController(Profile* profile);
+
 }  // namespace profiles
 
 #endif  // CHROME_BROWSER_PROFILES_PROFILES_STATE_H_