Fix use-after-move in //c/b/privacy/

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

Bug: 1122844
Change-Id: If9abd86031c1eaa915a2faa5cdbada40f3e6ee3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2560954
Auto-Submit: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Eric Orth <ericorth@chromium.org>
Reviewed-by: Eric Orth <ericorth@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831978}

chrome/browser/privacy/secure_dns_bridge.cc

@@ -59,7 +59,8 @@ void RunProbe(base::WaitableEvent* waiter,
       std::move(overrides),
       base::BindRepeating(&SystemNetworkContextManager::GetContext,
                           base::Unretained(manager)));
-  runner->RunProbe(base::BindOnce(
+  auto* const runner_ptr = runner.get();
+  runner_ptr->RunProbe(base::BindOnce(
       [](base::WaitableEvent* waiter, bool* success,
          std::unique_ptr<DnsProbeRunner> runner) {
         *success = runner->result() == DnsProbeRunner::CORRECT;