Expand documentation for URLLoaderFactoryGetter::CloneNetworkFactory.

It can be used for both network service enabled and disabled. The
factory also can't be sent to the renderer.

Change-Id: I443179fbb5dcb9e1325614e5bc04bf8fe20db2d9
Reviewed-on: https://chromium-review.googlesource.com/1195296Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Matt Falkenhagen <falken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587865}

content/browser/url_loader_factory_getter.h

@@ -60,9 +60,16 @@ class URLLoaderFactoryGetter
   CONTENT_EXPORT std::unique_ptr<network::SharedURLLoaderFactoryInfo>
   GetNetworkFactoryInfo();
 
-  // Called on the IO thread. Will clone the internal factory to the network
-  // service which doesn't support auto-reconnect after crash. Useful for
-  // one-off requests (e.g. A single navigation) to avoid additional mojo hop.
+  // Called on the IO thread. The factory obtained from here can only be used
+  // from the browser process. It must NOT be sent to a renderer process.
+  //
+  // When NetworkService is enabled, this clones the internal factory to the
+  // network service, which doesn't support auto-reconnect after crash. Useful
+  // for one-off requests (e.g. a single navigation) to avoid an additional Mojo
+  // hop.
+  //
+  // When NetworkService is disabled, this clones the non-NetworkService direct
+  // network factory.
   CONTENT_EXPORT void CloneNetworkFactory(
       network::mojom::URLLoaderFactoryRequest network_factory_request);