Revert of Pass per-frame task runners to Workers (when possible)

third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp

Index: third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp b/third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp
index acc4f517650b271c18a28ca8e425a3ee70fd5dd5..d30cd1dc2dd20e0dd7ee2a2b847a4f0f8bf1a46b 100644
--- a/third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp
+++ b/third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp
@@ -39,7 +39,6 @@
 #include "core/inspector/ConsoleMessage.h"
 #include "core/inspector/InspectorInstrumentation.h"
 #include "core/loader/FrameLoadRequest.h"
-#include "core/workers/ParentFrameTaskRunners.h"
 #include "core/workers/WorkerClients.h"
 #include "core/workers/WorkerGlobalScope.h"
 #include "core/workers/WorkerInspectorProxy.h"
@@ -256,8 +255,6 @@ void WebEmbeddedWorkerImpl::postMessageToPageInspector(const String& message)
 
 void WebEmbeddedWorkerImpl::postTaskToLoader(const WebTraceLocation& location, std::unique_ptr<ExecutionContextTask> task)
 {
-    // TODO(hiroshige,yuryu): Make this not use ExecutionContextTask and
-    // consider using m_mainThreadTaskRunners->getLoadingTaskRunner() instead.
     m_mainFrame->frame()->document()->postTask(location, std::move(task));
 }
 
@@ -439,12 +436,6 @@ void WebEmbeddedWorkerImpl::startWorkerThread()
 
     m_mainScriptLoader.clear();
 
-    // We have a dummy document here for loading but it doesn't really represent
-    // the document/frame of associated document(s) for this worker. Here we
-    // populate the task runners with null document not to confuse the frame
-    // scheduler (which will end up using the thread's default task runner).
-    m_mainThreadTaskRunners = ParentFrameTaskRunners::create(nullptr);
-
     m_workerGlobalScopeProxy = ServiceWorkerGlobalScopeProxy::create(*this, *document, *m_workerContextClient);
     m_loaderProxy = WorkerLoaderProxy::create(this);
     m_workerThread = ServiceWorkerThread::create(m_loaderProxy, *m_workerGlobalScopeProxy);