Remove unused thread.h include in trace_event_impl.h and fix IWUU.

chrome/browser/safe_browsing/protocol_manager_unittest.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 "chrome/browser/safe_browsing/protocol_manager.h"
 
 #include <memory>
 #include <vector>
 
+#include "base/message_loop/message_loop.h"
 #include "base/strings/stringprintf.h"
 #include "base/test/test_simple_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/time.h"
 #include "chrome/browser/safe_browsing/chunk.pb.h"
 #include "components/safe_browsing_db/safebrowsing.pb.h"
 #include "components/safe_browsing_db/util.h"
 #include "content/public/test/test_browser_thread.h"
 #include "google_apis/google_api_keys.h"
 #include "net/base/escape.h"
@@ skipping 1078 matching lines @@
 
   EXPECT_FALSE(pm->IsUpdateScheduled());
 
   // Invoke the AddChunksCallback to finish the update.
   runner_->RunPendingTasks();
 
   EXPECT_TRUE(pm->IsUpdateScheduled());
 }
 
 }  // namespace safe_browsing