Don't create redundant ThreadData for Worker Threads

base/threading/platform_thread_mac.mm

 // 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 "base/threading/platform_thread.h"
 
 #import <Foundation/Foundation.h>
 #include <mach/mach.h>
 #include <mach/mach_time.h>
 #include <mach/thread_policy.h>
@@ skipping 31 matching lines @@
     [NSThread detachNewThreadSelector:@selector(class)
                              toTarget:[NSObject class]
                            withObject:nil];
     multithreaded = YES;
 
     DCHECK([NSThread isMultiThreaded]);
   }
 }
 
 // static
-void PlatformThread::SetName(const std::string& name) {
+void PlatformThread::SetName(const std::string& name, bool is_worker_thread) {
   ThreadIdNameManager::GetInstance()->SetName(CurrentId(), name);
-  tracked_objects::ThreadData::InitializeThreadContext(name);
+  if (!is_worker_thread)
+    tracked_objects::ThreadData::InitializeThreadContext(name);
 
   // Mac OS X does not expose the length limit of the name, so
   // hardcode it.
   const int kMaxNameLength = 63;
   std::string shortened_name = name.substr(0, kMaxNameLength);
   // pthread_setname() fails (harmlessly) in the sandbox, ignore when it does.
   // See http://crbug.com/47058
   pthread_setname_np(shortened_name.c_str());
 }
 
@@ skipping 173 matching lines @@
                  static_cast<size_t>(stack_rlimit.rlim_cur));
   }
   return default_stack_size;
 #endif
 }
 
 void TerminateOnThread() {
 }
 
 }  // namespace base