Fix some flaky tests.

content/public/test/test_utils.h

 // 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.
 
 #ifndef CONTENT_PUBLIC_TEST_TEST_UTILS_H_
 #define CONTENT_PUBLIC_TEST_TEST_UTILS_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 71 matching lines @@
 void IsolateAllSitesForTesting(base::CommandLine* command_line);
 
 #if defined(OS_ANDROID)
 // Registers content/browser JNI bindings necessary for some types of tests.
 bool RegisterJniForTesting(JNIEnv* env);
 #endif
 
 // Helper class to Run and Quit the message loop. Run and Quit can only happen
 // once per instance. Make a new instance for each use. Calling Quit after Run
 // has returned is safe and has no effect.
+// Note that by default Quit does not quit immediately. If that is not what you
+// really need, pass QuitMode::IMMEDIATE in the constructor.
 class MessageLoopRunner : public base::RefCounted<MessageLoopRunner> {
  public:
-  MessageLoopRunner();
+  enum class QuitMode {
+    // Message loop stops after finishing the current task.
+    IMMEDIATE,
+
+    // Several generations of posted tasks are executed before stopping.
+    DEFERRED,
+  };
+
+  MessageLoopRunner(QuitMode mode = QuitMode::DEFERRED);
 
   // Run the current MessageLoop unless the quit closure
   // has already been called.
   void Run();
 
   // Quit the matching call to Run (nested MessageLoops are unaffected).
   void Quit();
 
   // Hand this closure off to code that uses callbacks to notify completion.
   // Example:
   //   scoped_refptr<MessageLoopRunner> runner = new MessageLoopRunner;
   //   kick_off_some_api(runner->QuitClosure());
   //   runner->Run();
   base::Closure QuitClosure();
 
   bool loop_running() const { return loop_running_; }
 
  private:
   friend class base::RefCounted<MessageLoopRunner>;
   ~MessageLoopRunner();
 
+  QuitMode quit_mode_;
+
   // True when the message loop is running.
   bool loop_running_;
 
   // True after closure returned by |QuitClosure| has been called.
   bool quit_closure_called_;
 
   base::RunLoop run_loop_;
 
   base::ThreadChecker thread_checker_;
 
@@ skipping 157 matching lines @@
   void WebContentsDestroyed() override;
 
   scoped_refptr<MessageLoopRunner> message_loop_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsDestroyedWatcher);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_TEST_TEST_UTILS_H_