Disable modifying extensions when in managed mode.

chrome/browser/resources/options2/chromeos/internet_detail.html

 <div id="details-internet-page" class="page" hidden>
   <div class="close-button"></div>
   <!-- Network header -->
   <div id="network-details-header">
     <div id="network-details-title"></div>
     <div id="network-details-subtitle">
       <span id="network-details-subtitle-status"></span>
       <span id="network-details-subtitle-separator"> - </span>
       <span id="network-details-subtitle-type"></span>
     </div>
@@ skipping 435 matching lines @@
             <button id="change-pin" i18n-content="changePinButton"></button>
             <span class="controlled-setting-indicator" data="simCardLockEnabled"
                 for="change-pin"></span>
           </div>
         </section>
       </div>
     </div>
     <div id="network-proxy-tab" class="subpages-tab-contents">
       <section>
         <div id="info-banner" hidden>
-          <span id="banner-icon" class="managed-prefs-icon"></span>
-          <span id="banner-text" class="managed-prefs-text"></span>
+          <span id="banner-icon" class="main-page-banner-icon"></span>
+          <span id="banner-text" class="main-page-banner-text"></span>
         </div>
         <div class="radio">
           <label>
             <input id="direct-proxy" type="radio" name="proxytype" value="1"
                 pref="cros.session.proxy.type">
             <span i18n-content="proxyDirectInternetConnection"></span>
           </label>
         </div>
         <div class="radio">
           <label>
@@ skipping 130 matching lines @@
       </button>
       <button id="details-internet-disconnect" i18n-content="disconnectButton">
       </button>
       <button id="activate-details" i18n-content="activateButton"></button>
       <button id="buyplan-details" i18n-content="buyplanButton"></button>
       <button id="view-account-details" i18n-content="viewAccountButton">
       </button>
     </div>
   </div>
 </div>