Implement the infrastructure of creating WorkerFetchContext in worker global scope.

third_party/WebKit/Source/core/loader/FrameFetchContext.cpp

Index: third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
diff --git a/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp b/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
index d0011ef61e5c6130560ce20b823ca28e77e11caa..f634a480de8d90c449a81dec289f0278e9cd5355 100644
--- a/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
+++ b/third_party/WebKit/Source/core/loader/FrameFetchContext.cpp
@@ -81,6 +81,7 @@
 #include "platform/scheduler/renderer/web_view_scheduler.h"
 #include "platform/weborigin/SchemeRegistry.h"
 #include "platform/wtf/Vector.h"
+#include "public/platform/Platform.h"
 #include "public/platform/WebCachePolicy.h"
 #include "public/platform/WebInsecureRequestPolicy.h"
 #include "public/platform/modules/serviceworker/WebServiceWorkerNetworkProvider.h"
@@ -903,6 +904,10 @@ bool FrameFetchContext::ShouldBlockFetchByMixedContentCheck(
                                                url, reporting_policy);
 }
 
+std::unique_ptr<WebURLLoader> FrameFetchContext::CreateURLLoader() {
+  return Platform::Current()->CreateURLLoader();
+}
+
 DEFINE_TRACE(FrameFetchContext) {
   visitor->Trace(document_loader_);
   BaseFetchContext::Trace(visitor);