Cancel keepalive request which has received response when detached

A request with keepalive set should continue working after the
associated FetchContext is detached, but no one cares its status after
it gets response. With this change such requests will be cancelled.

Bug: 764589
Change-Id: I9a5b9de6d658311bab27ab85fee3dea406457488
Reviewed-on: https://chromium-review.googlesource.com/885702Reviewed-by: Takeshi Yoshino <tyoshino@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532365}

third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp

@@ -1778,13 +1778,13 @@ void ResourceFetcher::StopFetchingInternal(StopFetchingTarget target) {
   HeapVector<Member<ResourceLoader>> loaders_to_cancel;
   for (const auto& loader : non_blocking_loaders_) {
     if (target == StopFetchingTarget::kIncludingKeepaliveLoaders ||
-        !loader->GetKeepalive()) {
+        !loader->ShouldBeKeptAliveWhenDetached()) {
       loaders_to_cancel.push_back(loader);
     }
   }
   for (const auto& loader : loaders_) {
     if (target == StopFetchingTarget::kIncludingKeepaliveLoaders ||
-        !loader->GetKeepalive()) {
+        !loader->ShouldBeKeptAliveWhenDetached()) {
       loaders_to_cancel.push_back(loader);
     }
   }

third_party/WebKit/Source/platform/loader/fetch/ResourceLoader.cpp

@@ -483,6 +483,13 @@ void ResourceLoader::DidReceiveResponse(
     std::unique_ptr<WebDataConsumerHandle> handle) {
   DCHECK(!web_url_response.IsNull());
 
+  if (Context().IsDetached()) {
+    // If the fetch context is already detached, we don't need further signals,
+    // so let's cancel the request.
+    HandleError(ResourceError::CancelledError(web_url_response.Url()));
+    return;
+  }
+
   Resource::Type resource_type = resource_->GetType();
 
   const ResourceRequest& initial_request = resource_->GetResourceRequest();
@@ -763,8 +770,9 @@ void ResourceLoader::ActivateCacheAwareLoadingIfNeeded(
   is_cache_aware_loading_activated_ = true;
 }
 
-bool ResourceLoader::GetKeepalive() const {
-  return resource_->GetResourceRequest().GetKeepalive();
+bool ResourceLoader::ShouldBeKeptAliveWhenDetached() const {
+  return resource_->GetResourceRequest().GetKeepalive() &&
+         resource_->GetResponse().IsNull();
 }
 
 }  // namespace blink

third_party/WebKit/Source/platform/loader/fetch/ResourceLoader.h

@@ -84,7 +84,7 @@ class PLATFORM_EXPORT ResourceLoader final
   }
 
   ResourceFetcher* Fetcher() { return fetcher_; }
-  bool GetKeepalive() const;
+  bool ShouldBeKeptAliveWhenDetached() const;
 
   // WebURLLoaderClient
   //