Implement the infrastructure of creating WorkerFetchContext in worker global scope.

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 6acd6833d14aa1989cea9188bbb255a3c6f07ea9..607114ee3a3210862afdc61e8a5b506ef44c5d96 100644
--- a/third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp
+++ b/third_party/WebKit/Source/web/WebEmbeddedWorkerImpl.cpp
@@ -38,6 +38,7 @@
 #include "core/inspector/ConsoleMessage.h"
 #include "core/loader/FrameLoadRequest.h"
 #include "core/loader/ThreadableLoadingContext.h"
+#include "core/loader/WorkerFetchContext.h"
 #include "core/probe/CoreProbes.h"
 #include "core/workers/ParentFrameTaskRunners.h"
 #include "core/workers/WorkerClients.h"
@@ -49,6 +50,7 @@
 #include "modules/serviceworkers/ServiceWorkerContainerClient.h"
 #include "modules/serviceworkers/ServiceWorkerThread.h"
 #include "platform/Histogram.h"
+#include "platform/RuntimeEnabledFeatures.h"
 #include "platform/SharedBuffer.h"
 #include "platform/heap/Handle.h"
 #include "platform/loader/fetch/SubstituteData.h"
@@ -60,6 +62,7 @@
 #include "platform/wtf/PtrUtil.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebURLRequest.h"
+#include "public/platform/WebWorkerFetchContext.h"
 #include "public/platform/modules/serviceworker/WebServiceWorkerNetworkProvider.h"
 #include "public/platform/modules/serviceworker/WebServiceWorkerProvider.h"
 #include "public/web/WebConsoleMessage.h"
@@ -433,6 +436,17 @@ void WebEmbeddedWorkerImpl::StartWorkerThread() {
       worker_clients,
       WTF::WrapUnique(worker_context_client_->CreateServiceWorkerProvider()));
 
+  if (RuntimeEnabledFeatures::offMainThreadFetchEnabled()) {
+    std::unique_ptr<WebWorkerFetchContext> web_worker_fetch_context =
+        WTF::WrapUnique(
+            worker_context_client_->CreateServiceWorkerFetchContext());
+    DCHECK(web_worker_fetch_context);
+    // TODO(horo): Set more information about the context (ex: DataSaverEnabled)
+    // to |web_worker_fetch_context|.
+    ProvideWorkerFetchContextToWorker(worker_clients,
+                                      std::move(web_worker_fetch_context));
+  }
+
   // We need to set the CSP to both the shadow page's document and the
   // ServiceWorkerGlobalScope.
   document->InitContentSecurityPolicy(