Reland "Remove unnecessary NetworkService flag check in ResourceDispatcher"

This reverts commit 826c708a.

Reason for revert: This was speculatively reverted but wasn't the culprit.

Original change's description:
> Revert "Remove unnecessary NetworkService flag check in ResourceDispatcher"
> 
> This reverts commit 3d493dc6.
> 
> Reason for revert: FindIt blamed this CL with 85% confidence.
> 
> Sorry. I don't see anything wrong with this CL, but I also don't see
> anything wrong with any other CL in the blamelist, so I'm starting
> here. See https://crbug.com/873015 for analysis.
> 
> Original change's description:
> > Remove unnecessary NetworkService flag check in ResourceDispatcher
> > 
> > blink::ServiceWorkerUtils::IsServicificationEnabled() checks
> > whether NetworkService is enabled, so we don't need the check
> > in ResourceDispatcher::StartAsync().
> > 
> > Bug: N/A
> > Change-Id: I06bab175489f42dc0cefa2a257806db29192eba1
> > Reviewed-on: https://chromium-review.googlesource.com/1168707
> > Reviewed-by: Makoto Shimazu <shimazu@chromium.org>
> > Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
> > Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#581828}
> 
> TBR=yhirano@chromium.org,bashi@chromium.org,shimazu@chromium.org
> 
> Change-Id: Ia89cf9c0523395c7b331482f39e708f283cbc3ec
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: N/A
> Reviewed-on: https://chromium-review.googlesource.com/1170402
> Reviewed-by: Matt Giuca <mgiuca@chromium.org>
> Commit-Queue: Matt Giuca <mgiuca@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#582023}

TBR=yhirano@chromium.org,bashi@chromium.org,mgiuca@chromium.org,shimazu@chromium.org

Change-Id: Ia3b4db0a6d9586d4febc3a16c1d6f8c987b124fb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: N/A
Reviewed-on: https://chromium-review.googlesource.com/1170622Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582082}

content/renderer/loader/resource_dispatcher.cc

@@ -722,8 +722,7 @@ int ResourceDispatcher::StartAsync(
   uint32_t options = network::mojom::kURLLoadOptionNone;
   // TODO(jam): use this flag for ResourceDispatcherHost code path once
   // MojoLoading is the only IPC code path.
-  if ((blink::ServiceWorkerUtils::IsServicificationEnabled() ||
-       base::FeatureList::IsEnabled(network::features::kNetworkService)) &&
+  if (blink::ServiceWorkerUtils::IsServicificationEnabled() &&
       request->fetch_request_context_type != REQUEST_CONTEXT_TYPE_FETCH) {
     // MIME sniffing should be disabled for a request initiated by fetch().
     options |= network::mojom::kURLLoadOptionSniffMimeType;