Remove unused WebThread based code for workers

content/child/blink_platform_impl.cc

Index: content/child/blink_platform_impl.cc
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index ca4a2400c60eb79c371b66a080785b73e42683c9..015c8e759ec42ff63dc5afa3a85b370af2c109c5 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -933,16 +933,6 @@ void BlinkPlatformImpl::didStopWorkerRunLoop(
   worker_task_runner->OnWorkerRunLoopStopped(runLoop);
 }
 
-void BlinkPlatformImpl::didStartWorkerThread(blink::WebThread* thread) {
-  WorkerTaskRunner* worker_task_runner = WorkerTaskRunner::Instance();
-  worker_task_runner->OnWorkerThreadStarted(thread);
-}
-
-void BlinkPlatformImpl::didStopWorkerThread(blink::WebThread* thread) {
-  WorkerTaskRunner* worker_task_runner = WorkerTaskRunner::Instance();
-  worker_task_runner->OnWorkerThreadStopped(thread);
-}
-
 blink::WebCrypto* BlinkPlatformImpl::crypto() {
   return &web_crypto_;
 }