Do not run a nested loop in content::DeferredQuitRunLoop.

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 30 matching lines @@
 // to what they were originally. Prefer this over MessageLoop::Run for in
 // process browser tests that need to block until a condition is met.
 void RunMessageLoop();
 
 // Variant of RunMessageLoop that takes RunLoop.
 void RunThisRunLoop(base::RunLoop* run_loop);
 
 // Turns on nestable tasks, runs all pending tasks in the message loop,
 // then resets nestable tasks to what they were originally. Prefer this
 // over MessageLoop::RunAllPending for in process browser tests to run
-// all pending tasks.
+// all pending tasks. Can only be called from the UI thread.
 void RunAllPendingInMessageLoop();
 
 // Blocks the current thread until all the pending messages in the loop of the
-// thread |thread_id| have been processed.
+// thread |thread_id| have been processed. Can only be called from the UI
+// thread.
 void RunAllPendingInMessageLoop(BrowserThread::ID thread_id);
 
 // Runs until both the blocking pool and the current message loop are empty
 // (have no more scheduled tasks) and no tasks are running.
 void RunAllBlockingPoolTasksUntilIdle();
 
 // Get task to quit the given RunLoop. It allows a few generations of pending
 // tasks to run as opposed to run_loop->QuitClosure().
 base::Closure GetQuitTaskForRunLoop(base::RunLoop* run_loop);
 
@@ skipping 216 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_