Don't create redundant ThreadData for Worker Threads

base/threading/platform_thread_mac.mm

Index: base/threading/platform_thread_mac.mm
diff --git a/base/threading/platform_thread_mac.mm b/base/threading/platform_thread_mac.mm
index 51f3621af2d999a73295967bf14db42425b90302..954a2bc64043a9f6805779298364e6927c0dfa88 100644
--- a/base/threading/platform_thread_mac.mm
+++ b/base/threading/platform_thread_mac.mm
@@ -49,9 +49,10 @@ void InitThreading() {
 }
 
 // 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.