Network config UI fixes

This CL:
* Fixes a Polymer2 bug where networkProxy.isShared_ was called while
  networkProperties was undefined without checking, causing a console
  error.
* Fixes a DCHECK in the ONC code when configuring Ethernet nameservers
  or IP config properties.
* Also updates NULL -> nullptr in onc_translation_tables.cc.

Bug: issue 931845
Change-Id: I87a953a0b7779f0d7f4538a5b9e8a5a95f9d5235
Reviewed-on: https://chromium-review.googlesource.com/c/1471307Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632010}

chromeos/network/onc/onc_translator_onc_to_shill.cc

@@ -337,9 +337,9 @@ void LocalTranslator::TranslateNetworkConfiguration() {
   onc_object_->GetStringWithoutPathExpansion(::onc::network_config::kType,
                                              &type);
 
-  // Set the type except for Ethernet which is set in TranslateEthernet.
-  if (type != ::onc::network_type::kEthernet)
-    TranslateWithTableAndSet(type, kNetworkTypeTable, shill::kTypeProperty);
+  // Note; The Ethernet type might be overridden to EthernetEap in
+  // TranslateEthernet if Ethernet specific properties are provided.
+  TranslateWithTableAndSet(type, kNetworkTypeTable, shill::kTypeProperty);
 
   // Shill doesn't allow setting the name for non-VPN networks.
   if (type == ::onc::network_type::kVPN)

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

@@ -452,8 +452,11 @@ Polymer({
    * @private
    */
   isShared_: function() {
-    return this.networkProperties.Source == 'Device' ||
-        this.networkProperties.Source == 'DevicePolicy';
+    if (!this.networkProperties) {
+      return false;
+    }
+    const source = this.networkProperties.Source;
+    return source == 'Device' || source == 'DevicePolicy';
   },
 
   /**