MD-Settings: Adds an a11y label to most toggle buttons.

chrome/browser/resources/settings/date_time_page/date_time_page.html

 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/web_ui_listener_behavior.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_pref_indicator.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-toggle-button/paper-toggle-button.html">
 <link rel="import" href="../controls/settings_dropdown_menu.html">
 <link rel="import" href="../controls/settings_toggle_button.html">
 <link rel="import" href="../i18n_setup.html">
 <link rel="import" href="../prefs/prefs_behavior.html">
@@ skipping 12 matching lines @@
         -webkit-margin-start: var(--checkbox-spacing);
       }
     </style>
     <div class="settings-box first">
       <settings-dropdown-menu pref="{{prefs.cros.system.timezone}}"
           menu-options="[[timeZoneList_]]"
           disabled="[[timeZoneAutoDetect_]]">
       </settings-dropdown-menu>
     </div>
     <div class="settings-box continuation">
-      <div class="start">$i18n{timeZoneGeolocation}</div>
+      <div id="timezoneGeolocateToggleLabel" class="start">
+        $i18n{timeZoneGeolocation}
+      </div>
       <template is="dom-if" if="[[hasTimeZoneAutoDetectPolicy_]]" restamp>
         <cr-policy-pref-indicator pref="[[fakeTimeZonePolicyPref_]]">
         </cr-policy-pref-indicator>
       </template>
       <paper-toggle-button
           id="timeZoneAutoDetect"
+          aria-labelledby="timezoneGeolocateToggleLabel"
           checked="[[timeZoneAutoDetect_]]"
           disabled="[[hasTimeZoneAutoDetectPolicy_]]"
           on-change="onTimeZoneAutoDetectChange_">
       </paper-toggle-button>
     </div>
     <div class="settings-box continuation">
       <settings-toggle-button class="start"
           pref="{{prefs.settings.clock.use_24hour_clock}}"
           label="$i18n{use24HourClock}">
       </settings-toggle-button>
     </div>
     <div class="settings-box" id="setDateTime" actionable
         on-tap="onSetDateTimeTap_" hidden$="[[!canSetDateTime_]]">
       <div class="start">$i18n{setDateTime}</div>
       <button class="subpage-arrow" is="paper-icon-button-light"
           aria-label="$i18n{setDateTime}"></button>
     </div>
   </template>
   <script src="date_time_page.js"></script>
 </dom-module>