Update from https://crrev.com/333737

base/threading/simple_thread.cc

 // Copyright (c) 2010 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 "base/threading/simple_thread.h"
 
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_restrictions.h"
@@ skipping 11 matching lines @@
       thread_(), event_(true, false), tid_(0), joined_(false) {
 }
 
 SimpleThread::~SimpleThread() {
   DCHECK(HasBeenStarted()) << "SimpleThread was never started.";
   DCHECK(HasBeenJoined()) << "SimpleThread destroyed without being Join()ed.";
 }
 
 void SimpleThread::Start() {
   DCHECK(!HasBeenStarted()) << "Tried to Start a thread multiple times.";
-  bool success = PlatformThread::Create(options_.stack_size(), this, &thread_);
+  bool success;
+  if (options_.priority() == ThreadPriority::NORMAL) {
+    success = PlatformThread::Create(options_.stack_size(), this, &thread_);
+  } else {
+    success = PlatformThread::CreateWithPriority(options_.stack_size(), this,
+                                                 &thread_, options_.priority());
+  }
   DCHECK(success);
   base::ThreadRestrictions::ScopedAllowWait allow_wait;
   event_.Wait();  // Wait for the thread to complete initialization.
 }
 
 void SimpleThread::Join() {
   DCHECK(HasBeenStarted()) << "Tried to Join a never-started thread.";
   DCHECK(!HasBeenJoined()) << "Tried to Join a thread multiple times.";
   PlatformThread::Join(thread_);
   joined_ = true;
@@ skipping 107 matching lines @@
 
     // A NULL delegate pointer signals us to quit.
     if (!work)
       break;
 
     work->Run();
   }
 }
 
 }  // namespace base