Fix some flaky tests.

content/public/test/browser_test_utils.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/public/test/browser_test_utils.h"
 
 #include <stddef.h>
 #include <tuple>
 #include <utility>
 
@@ skipping 1298 matching lines @@
 }
 
 void DOMMessageQueue::ClearQueue() {
   message_queue_ = std::queue<std::string>();
 }
 
 bool DOMMessageQueue::WaitForMessage(std::string* message) {
   DCHECK(message);
   if (message_queue_.empty()) {
     // This will be quit when a new message comes in.
-    message_loop_runner_ = new MessageLoopRunner;
+    message_loop_runner_ =
+        new MessageLoopRunner(MessageLoopRunner::QuitMode::IMMEDIATE);
     message_loop_runner_->Run();
   }
   // The queue should not be empty, unless we were quit because of a timeout.
   if (message_queue_.empty())
     return false;
   *message = message_queue_.front();
   message_queue_.pop();
   return true;
 }
 
@@ skipping 437 matching lines @@
 
   std::string ascii_message = base::UTF16ToASCII(message);
   if (base::MatchPattern(ascii_message, filter_)) {
     message_ = ascii_message;
     message_loop_runner_->Quit();
   }
   return false;
 }
 
 }  // namespace content