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 22c407438ef4e05f82f87dab5525d163671879d2..2497aa406ecea4a222fadadf1715acb33ce44a05 100644
--- a/third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp
+++ b/third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp
@@ -39,6 +39,7 @@
 #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"
@@ -255,6 +256,8 @@ void WebEmbeddedWorkerImpl::postMessageToPageInspector(const String& message)
 
 void WebEmbeddedWorkerImpl::postTaskToLoader(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(BLINK_FROM_HERE, std::move(task));
 }
 
@@ -436,6 +439,12 @@ 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);