DataSaver support for off-main-thread-fetch

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

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/loader/WorkerFetchContext.h"
 
 #include "core/frame/Deprecation.h"
 #include "core/frame/UseCounter.h"
 #include "core/workers/WorkerClients.h"
 #include "core/workers/WorkerGlobalScope.h"
@@ skipping 155 matching lines @@
                                         RedirectType) {
   request.OverrideLoadingIPCType(WebURLRequest::LoadingIPCType::kMojo);
   WrappedResourceRequest webreq(request);
   web_context_->WillSendRequest(webreq);
 }
 
 RefPtr<WebTaskRunner> WorkerFetchContext::LoadingTaskRunner() const {
   return loading_task_runner_;
 }
 
+void WorkerFetchContext::AddAdditionalRequestHeaders(ResourceRequest& request,
+                                                     FetchResourceType type) {
+  BaseFetchContext::AddAdditionalRequestHeaders(request, type);
+
+  // The remaining modifications are only necessary for HTTP and HTTPS.
+  if (!request.Url().IsEmpty() && !request.Url().ProtocolIsInHTTPFamily())
+    return;
+
+  if (web_context_->IsDataSaverEnabled())
+    request.SetHTTPHeaderField("Save-Data", "on");
+}
+
 DEFINE_TRACE(WorkerFetchContext) {
   visitor->Trace(worker_global_scope_);
   visitor->Trace(resource_fetcher_);
   BaseFetchContext::Trace(visitor);
 }
 
 void ProvideWorkerFetchContextToWorker(
     WorkerClients* clients,
     std::unique_ptr<WebWorkerFetchContext> web_context) {
   DCHECK(clients);
   WorkerFetchContextHolder::ProvideTo(
       *clients, WorkerFetchContextHolder::SupplementName(),
       new WorkerFetchContextHolder(std::move(web_context)));
 }
 
 }  // namespace blink