Implement the infrastructure of creating WorkerFetchContext in worker global scope.

third_party/WebKit/public/web/WebFrameClient.h

Index: third_party/WebKit/public/web/WebFrameClient.h
diff --git a/third_party/WebKit/public/web/WebFrameClient.h b/third_party/WebKit/public/web/WebFrameClient.h
index b32fe0821df8bc716529a01e726c54a87fd298f4..0a71890a99074abef30e3972dd66f5a974a6cc9c 100644
--- a/third_party/WebKit/public/web/WebFrameClient.h
+++ b/third_party/WebKit/public/web/WebFrameClient.h
@@ -65,6 +65,7 @@
 #include "public/platform/WebStorageQuotaType.h"
 #include "public/platform/WebURLError.h"
 #include "public/platform/WebURLRequest.h"
+#include "public/platform/WebWorkerFetchContext.h"
 #include "v8/include/v8.h"
 
 namespace blink {
@@ -146,6 +147,13 @@ class BLINK_EXPORT WebFrameClient {
     return 0;
   }
 
+  // Returns a new WebWorkerFetchContext for a dedicated worker. Ownership of
+  // the returned object is transferred to the caller. This is used only when
+  // off-main-thread-fetch is enabled.
+  virtual std::unique_ptr<WebWorkerFetchContext> CreateWorkerFetchContext() {
+    return nullptr;
+  }
+
   // Create a new WebPopupMenu. In the "createExternalPopupMenu" form, the
   // client is responsible for rendering the contents of the popup menu.
   virtual WebExternalPopupMenu* CreateExternalPopupMenu(