Signin/OAuth: Create an AccessTokenFetcher helper class

components/signin/core/browser/fake_signin_manager.h

Index: components/signin/core/browser/fake_signin_manager.h
diff --git a/components/signin/core/browser/fake_signin_manager.h b/components/signin/core/browser/fake_signin_manager.h
index 83b2728e18957f8725b7f3b7fe47a2593fad7694..452984ed1df5cb272dbc82e65ce5632246a853c3 100644
--- a/components/signin/core/browser/fake_signin_manager.h
+++ b/components/signin/core/browser/fake_signin_manager.h
@@ -17,14 +17,20 @@
 // SigninManagerForTesting to ensure that the right type for their platform is
 // used.
 
-// Overrides InitTokenService to do-nothing in tests.
 class FakeSigninManagerBase : public SigninManagerBase {
  public:
   FakeSigninManagerBase(SigninClient* client,
                         AccountTrackerService* account_tracker_service);
   ~FakeSigninManagerBase() override;
 
+  bool AuthInProgress() const override;
+
+  void SetAuthInProgress(bool auth_in_progress);
+
   void SignIn(const std::string& account_id);
+
+ private:
+  bool auth_in_progress_;
 };
 
 #if !defined(OS_CHROMEOS)