[TimeZoneMonitor] Decouple renderer side impl from content to blink.

third_party/WebKit/Source/core/workers/WorkerThread.cpp

Index: third_party/WebKit/Source/core/workers/WorkerThread.cpp
diff --git a/third_party/WebKit/Source/core/workers/WorkerThread.cpp b/third_party/WebKit/Source/core/workers/WorkerThread.cpp
index f03dfb3508ee3a50d82574df321b0017c5fc9281..55d3511f5b1dea34fe7a87259e5a5a672532e585 100644
--- a/third_party/WebKit/Source/core/workers/WorkerThread.cpp
+++ b/third_party/WebKit/Source/core/workers/WorkerThread.cpp
@@ -153,11 +153,6 @@ static Mutex& threadSetMutex() {
   return mutex;
 }
 
-static HashSet<WorkerThread*>& workerThreads() {
-  DEFINE_STATIC_LOCAL(HashSet<WorkerThread*>, threads, ());
-  return threads;
-}
-
 WorkerThreadLifecycleContext::WorkerThreadLifecycleContext() {
   DCHECK(isMainThread());
 }
@@ -320,6 +315,12 @@ unsigned WorkerThread::workerThreadCount() {
   return workerThreads().size();
 }
 
+HashSet<WorkerThread*>& WorkerThread::workerThreads() {
+  DCHECK(isMainThread());
+  DEFINE_STATIC_LOCAL(HashSet<WorkerThread*>, threads, ());
+  return threads;
+}
+
 PlatformThreadId WorkerThread::platformThreadId() {
   if (!m_requestedToStart)
     return 0;