Hide Shared Modules behind "Developer Mode"

BUG=420670

Review URL: https://codereview.chromium.org/773363002

Cr-Commit-Position: refs/heads/master@{#308388}

chrome/browser/resources/extensions/extension_list.js

@@ -449,6 +449,7 @@ cr.define('options', function() {
       }
 
       if (extension.dependentExtensions.length > 0) {
+        node.classList.add('developer-extras');
         var dependentMessage =
             node.querySelector('.dependent-extensions-message');
         dependentMessage.hidden = false;

chrome/browser/resources/extensions/extensions.html

@@ -253,7 +253,7 @@
   </div>
   <li class="dependent-list-item">
     <span class="dep-extension-title"></span>
-    <ul class="developer-extras">
+    <ul>
       <li>
         <span i18n-content="extensionSettingsExtensionId"></span>
         <span class="dep-extension-id"></span>