[CrOS Tether] Add tether settings section to the MD settings page.

chrome/browser/resources/settings/internet_page/network_summary_item.js

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview Polymer element for displaying the network state for a specific
  * type and a list of networks for that type.
  */
 
 /** @typedef {chrome.networkingPrivate.DeviceStateProperties} */
@@ skipping 170 matching lines @@
 
   /**
    * @param {!DeviceStateProperties} deviceState
    * @return {string}
    * @private
    */
   getToggleA11yString_: function(deviceState) {
     if (!this.enableToggleIsVisible_(deviceState))
       return '';
     switch (deviceState.Type) {
+      case CrOnc.Type.TETHER:
+        return this.i18n('internetToggleTetherA11yLabel');
       case CrOnc.Type.CELLULAR:
         return this.i18n('internetToggleMobileA11yLabel');
       case CrOnc.Type.WI_FI:
         return this.i18n('internetToggleWiFiA11yLabel');
       case CrOnc.Type.WI_MAX:
         return this.i18n('internetToggleWiMAXA11yLabel');
     }
     assertNotReached();
     return '';
   },
 
   /**
    * @return {boolean}
    * @private
    */
   showDetailsIsVisible_: function() {
     return this.deviceIsEnabled_(this.deviceState) &&
         (!!this.activeNetworkState.GUID || this.networkStateList.length > 0);
   },
 
   /**
    * @return {boolean}
    * @private
    */
   shouldShowList_: function() {
     var minlen = (this.deviceState.Type == CrOnc.Type.WI_FI ||
-                  this.deviceState.Type == CrOnc.Type.VPN) ?
+                  this.deviceState.Type == CrOnc.Type.VPN ||
+                  this.deviceState.Type == CrOnc.Type.TETHER) ?
         1 :
         2;
     return this.networkStateList.length >= minlen;
   },
 
   /**
    * @param {!Event} event The enable button event.
    * @private
    */
   onShowDetailsTap_: function(event) {
@@ skipping 33 matching lines @@
    */
   onDeviceEnabledTap_: function(event) {
     var deviceIsEnabled = this.deviceIsEnabled_(this.deviceState);
     var type = this.deviceState ? this.deviceState.Type : '';
     this.fire(
         'device-enabled-toggled', {enabled: !deviceIsEnabled, type: type});
     // Make sure this does not propagate to onDetailsTap_.
     event.stopPropagation();
   },
 });