signin: pull basic SigninManager functionality into new SigninManagerBase class.

chrome/browser/extensions/api/identity/identity_api.h

Index: chrome/browser/extensions/api/identity/identity_api.h
diff --git a/chrome/browser/extensions/api/identity/identity_api.h b/chrome/browser/extensions/api/identity/identity_api.h
index de9ecf662c179d6ef1ad9b552b665ceb75ab3340..f62389b3c04570a17558732d829466b7309a38f2 100644
--- a/chrome/browser/extensions/api/identity/identity_api.h
+++ b/chrome/browser/extensions/api/identity/identity_api.h
@@ -22,6 +22,7 @@ class GetAuthTokenFunctionTest;
 class MockGetAuthTokenFunction;
 class GoogleServiceAuthError;
 class Profile;
+class SigninManagerBase;
 
 namespace extensions {
 
@@ -156,7 +157,7 @@ class IdentityAPI : public ProfileKeyedAPI,
   static const bool kServiceIsNULLWhileTesting = true;
 
   Profile* profile_;
-  SigninManager* signin_manager_;
+  SigninManagerBase* signin_manager_;
   GoogleServiceAuthError error_;
   // Used to listen to notifications from the TokenService.
   content::NotificationRegistrar registrar_;