Override SigninManager::SignOut if force-signin is enabled.

components/signin/core/browser/signin_manager.h

Index: components/signin/core/browser/signin_manager.h
diff --git a/components/signin/core/browser/signin_manager.h b/components/signin/core/browser/signin_manager.h
index f9b6be7b2b208176776579e806569ff4e60edd30..92e9ff587eca25c491ee14f326b9db83e7b2f22f 100644
--- a/components/signin/core/browser/signin_manager.h
+++ b/components/signin/core/browser/signin_manager.h
@@ -147,6 +147,10 @@ class SigninManager : public SigninManagerBase,
   // Flag saying whether signing out is allowed.
   bool prohibit_signout_;
 
+  // The sign out process which is started by SigninClient::PreSignOut()
+  virtual void DoSignOut(signin_metrics::ProfileSignout signout_source_metric,
+                         signin_metrics::SignoutDelete signout_delete_metric);
+
  private:
   enum SigninType { SIGNIN_TYPE_NONE, SIGNIN_TYPE_WITH_REFRESH_TOKEN };