Removing a stale comment for URLLoaderFactoryParams vs navigation race.

After r807668, the RenderFrameHostImpl::UpdateSubresourceLoaderFactories
is no longer affected by the race with an in-flight navigation.
Therefore, this CL removes the stale comment that talked about the race.

Note that in UpdateSubresourceLoaderFactories it was possible to
determine that the in-flight navigation should be preferred over the
last committed navigation (for calculating the URLLoaderFactoryParams),
because UpdateSubresourceLoaderFactories sends the new factory *to* the
renderer (and therefore the renderer will receive the new factory
*after* the in-flight navigation commits).  Such determination is not
possible for RenderFrameHostImpl::CreateNetworkServiceDefaultFactory
because it is exposed via //content/public API and therefore we don't
know if the caller will use the results of
CreateNetworkServiceDefaultFactory for 1) sending an IPC *to* the
renderer or 2) responding to an IPC sent *from* the renderer.  Therefore
the CL leaves unchanged the old comment and behavior of
CreateNetworkServiceDefaultFactory.

Bug: 1056949
Change-Id: Ib7689891b3b9b4bad6b4e66fe0997ece358ef8ca
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2419331Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#808459}

content/browser/renderer_host/render_frame_host_impl.cc

@@ -3688,10 +3688,6 @@ void RenderFrameHostImpl::UpdateSubresourceLoaderFactories() {
   DCHECK(!IsOutOfProcessNetworkService() ||
          network_service_disconnect_handler_holder_.is_bound());
 
-  // We use the last committed Origin and ClientSecurityState. If the caller
-  // wanted a factory associated to a navigation about to commit, the params
-  // generated won't be correct. There is no good way of fixing this before
-  // RenderDocumentHost (ie swapping RenderFrameHost on each navigation).
   mojo::PendingRemote<network::mojom::URLLoaderFactory> default_factory_remote;
   bool bypass_redirect_checks = false;
   if (recreate_default_url_loader_factory_after_network_service_crash_) {