MD Settings: clarify "controlled by" logic

chrome/browser/resources/settings/controls/settings_input.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-input/paper-input.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_pref_behavior.html">
 <link rel="import" href="chrome://resources/cr_elements/policy/cr_policy_pref_indicator.html">
 <link rel="import" href="/controls/pref_control_behavior.html">
 
 <dom-module id="settings-input">
   <template>
     <style>
       :host {
         -webkit-margin-start: 4px;
         cursor: auto;
         display: inline-block;
       }
     </style>
     <div id="outerDiv" class="layout horizontal center">
       <paper-input id="input" auto-validate value="{{value}}"
           error-message="[[errorMessage]]" label="[[label]]"
           no-label-float="[[noLabelFloat]]" pattern="[[pattern]]"
           readonly$="[[readonly]]" required="[[required]]" type="[[type]]"
           on-blur="onBlur_" disabled="[[isDisabled_(disabled, pref)]]"
           stop-keyboard-event-propagation$="[[stopKeyboardEventPropagation]]"
           tabindex$="[[getTabindex_(canTab)]]">
       </paper-input>
-      <template is="dom-if" if="[[pref.policySource]]">
+      <template is="dom-if" if="[[pref.contolledBy]]">
         <cr-policy-pref-indicator pref="[[pref]]"></cr-policy-pref-indicator>
       </template>
     </div>
   </template>
   <script src="settings_input.js"></script>
 </dom-module>