Fix use-after-move in //c/b/ui/startup/

Fix use-after-move (potential) bugs found by the
"bugprone-use-after-move" clang-tidy check.

Bug: 1122844
Change-Id: Ie05076f5f7ad9543e4e6a45eb95a6847da0e66c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2560119
Auto-Submit: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Tien Mai <tienmai@chromium.org>
Reviewed-by: Tien Mai <tienmai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834691}

chrome/browser/ui/startup/credential_provider_signin_dialog_win.cc

@@ -126,7 +126,8 @@ void HandleSigninCompleteForGcpwLogin(
     // deleted once it is finished.
     auto fetcher = std::make_unique<CredentialProviderSigninInfoFetcher>(
         refresh_token, url_loader_factory);
-    fetcher->SetCompletionCallbackAndStart(
+    auto* const fetcher_ptr = fetcher.get();
+    fetcher_ptr->SetCompletionCallbackAndStart(
         access_token, additional_mdm_oauth_scopes,
         base::BindOnce(&HandleAllGcpwInfoFetched, std::move(keep_alive),
                        std::move(fetcher), std::move(signin_result)));