Chrome OS Network UI: forget selected network when it disappears from the list.

This CL fixes error message:

    Error in response to networkingPrivate.getNetworks: TypeError: Cannot read
    property 'GUID' of null", source: chrome://oobe/oobe (0)

and clears default network if it disappears from the list of networks.

Bug: 793262
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ia72e650b73202de56b8ec842dbcee81f65366793
Reviewed-on: https://chromium-review.googlesource.com/822171
Commit-Queue: Alexander Alekseev <alemate@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524287}

chrome/browser/resources/chromeos/login/oobe_welcome.js

@@ -326,7 +326,7 @@ Polymer({
    */
   onDefaultNetworkChanged_: function(event) {
     var state = event.detail;
-    this.defaultNetworkGuid_ = state.GUID;
+    this.defaultNetworkGuid_ = (state ? state.GUID : '');
     this.isConnected_ =
         !!state && state.ConnectionState == CrOnc.ConnectionState.CONNECTED;
     if (!state || state.GUID != this.networkLastSelectedGuid_)
@@ -346,6 +346,7 @@ Polymer({
    */
   onNetworkListNetworkItemSelected_: function(event) {
     var state = event.detail;
+    assert(state);
     // If the user has not previously made a selection and the default network
     // is selected and connected, continue to the next screen.
     if (this.networkLastSelectedGuid_ == '' &&
@@ -359,7 +360,10 @@ Polymer({
     // is pending connection attempt. So even if new selection is currently
     // connected, it may get disconnected at any time.
     // So just send one more connection request to cancel current attempts.
-    this.networkLastSelectedGuid_ = state.GUID;
+    this.networkLastSelectedGuid_ = (state ? state.GUID : '');
+
+    if (!state)
+      return;
 
     var self = this;
     var networkStateCopy = Object.assign({}, state);

chrome/browser/resources/chromeos/network_ui/network_ui.js

@@ -268,6 +268,7 @@ var NetworkUI = (function() {
    * @return {!HTMLTableRowElement} The created tr element for the expanded row.
    */
   var createExpandedRow = function(state, baseRow) {
+    assert(state);
     var guid = state.GUID || '';
     var expandedRow = createTableRowElement();
     expandedRow.className = 'state-table-row';

ui/webui/resources/cr_elements/chromeos/network/compiled_resources2.gyp

@@ -44,6 +44,7 @@
     {
       'target_name': 'cr_network_select',
       'dependencies': [
+        '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:util',
         '<(EXTERNS_GYP):networking_private',
         'cr_network_list_types',
         'cr_onc_types',

ui/webui/resources/cr_elements/chromeos/network/cr_network_select.js

@@ -166,10 +166,18 @@ Polymer({
                             CrOnc.ConnectionState.CONNECTED) ?
         this.networkStateList_[0] :
         null;
-    if (defaultState.GUID != this.defaultStateGuid_) {
-      this.defaultStateGuid_ = defaultState.GUID;
-      this.fire('default-network-changed', defaultState);
-    }
+
+    if (!defaultState && !this.defaultStateGuid_)
+      return;
+
+    // defaultState.GUID must never be empty.
+    assert(!defaultState || defaultState.GUID);
+
+    if (defaultState && defaultState.GUID == this.defaultStateGuid_)
+      return;
+
+    this.defaultStateGuid_ = defaultState ? defaultState.GUID : '';
+    this.fire('default-network-changed', defaultState);
   },
 
   /**