Implement the infrastructure of creating WorkerFetchContext in worker global scope.

third_party/WebKit/Source/web/DedicatedWorkerMessagingProxyProviderImpl.cpp

Index: third_party/WebKit/Source/web/DedicatedWorkerMessagingProxyProviderImpl.cpp
diff --git a/third_party/WebKit/Source/web/DedicatedWorkerMessagingProxyProviderImpl.cpp b/third_party/WebKit/Source/web/DedicatedWorkerMessagingProxyProviderImpl.cpp
index cf0153e0110d1db11f297b6e16b069a7c93852cc..bbfa0c8d9104078bcddf99e7aa562165087ba93a 100644
--- a/third_party/WebKit/Source/web/DedicatedWorkerMessagingProxyProviderImpl.cpp
+++ b/third_party/WebKit/Source/web/DedicatedWorkerMessagingProxyProviderImpl.cpp
@@ -31,10 +31,12 @@
 #include "web/DedicatedWorkerMessagingProxyProviderImpl.h"
 
 #include "core/dom/Document.h"
+#include "core/loader/WorkerFetchContext.h"
 #include "core/workers/DedicatedWorkerMessagingProxy.h"
 #include "core/workers/Worker.h"
 #include "core/workers/WorkerClients.h"
 #include "platform/wtf/PtrUtil.h"
+#include "public/platform/Platform.h"
 #include "public/platform/WebContentSettingsClient.h"
 #include "public/platform/WebString.h"
 #include "public/web/WebFrameClient.h"
@@ -67,6 +69,15 @@ DedicatedWorkerMessagingProxyProviderImpl::CreateWorkerMessagingProxy(
         worker_clients,
         WTF::WrapUnique(
             web_frame->Client()->CreateWorkerContentSettingsClientProxy()));
+    std::unique_ptr<WebWorkerFetchContext> web_worker_fetch_context =
+        Platform::Current()->CreateWorkerFetchContext();
+    // |web_worker_fetch_context| is null if off-main-thread-fetch is disabled.

[nhiroki, 2017/04/18 07:56:41]

If possible, I'd prefer to avoid checking the feature availability by a return
value of the creation method. If it's determined only by the feature flag, how
about checking it like this?

if (base::FeatureList::IsEnabled(kOffMainThreadFetch)) {
  std::unique_ptr<WebWorkerFetchContext> web_worker_fetch_context =
      Platform::Current()->CreateWorkerFetchContext();
  DCHECK(web_worker_fetch_context);
  ProvideWorkerFetchContextToWorker(
      worker_clients, std::move(web_worker_fetch_context));
}

[horo, 2017/04/18 12:53:34]

Done.

+    if (web_worker_fetch_context) {
+      // TODO(horo): Set more information about the context (ex: Service Worker
+      // provider ID) to |web_worker_fetch_context|.
+      ProvideWorkerFetchContextToWorker(worker_clients,
+                                        std::move(web_worker_fetch_context));

[kinuko, 2017/04/18 08:35:37]

I really don't think we need to use supplement here but can just pass it as
WorkerThreadStartupData or something like that, though, it might end up
requiring more changes (I quickly searched but current code setting is not very
convenient for us to do that).  It doesn't need to be addressed in this CL but
you can probably chat with nhiroki@ about that.

[horo, 2017/04/18 12:53:34]

Acknowledged.

+    }
     // FIXME: call provideServiceWorkerContainerClientToWorker here when we
     // support ServiceWorker in dedicated workers (http://crbug.com/371690)
     return new DedicatedWorkerMessagingProxy(worker, worker_clients);