Settings: Network: Fix CrNetworkProxy.isShared_ for mojo

Bug: 1032339
Change-Id: Iae5891afdb72391b0ba5844dac48867dc045eae0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1960069Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#723591}

ui/webui/resources/cr_components/chromeos/network/network_proxy.js

@@ -501,7 +501,8 @@ Polymer({
       return false;
     }
     const source = this.managedProperties.source;
-    return source == 'Device' || source == 'DevicePolicy';
+    return source == chromeos.networkConfig.mojom.OncSource.kDevice ||
+        source == chromeos.networkConfig.mojom.OncSource.kDevicePolicy;
   },
 
   /**