MD Settings: implement support for extension-controlled startup URLs

chrome/browser/resources/settings/on_startup_page/startup_url_entry.html

 <link rel="import" href="chrome://resources/cr_elements/cr_action_menu/cr_action_menu.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_lazy_render/cr_lazy_render.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="/on_startup_page/startup_urls_page_browser_proxy.html">
 <link rel="import" href="/settings_shared_css.html">
 
 <dom-module id="settings-startup-url-entry">
   <template>
     <style include="settings-shared">
       .hide-overflow {
         overflow: hidden;
       }
     </style>
     <div class="list-item">
       <div class="favicon-image"
           style="background-image: [[getIconSet_(model.url)]]">
       </div>
       <div class="middle hide-overflow">
         <div class="text-elide">[[model.title]]</div>
         <div class="text-elide secondary">[[model.url]]</div>
       </div>
-      <paper-icon-button id="dots" icon="cr:more-vert" tabindex$="[[tabindex]]"
-          on-tap="onDotsTap_">
-      </paper-icon-button>
-      <template is="cr-lazy-render" id="menu">
-        <dialog is="cr-action-menu">
-          <button class="dropdown-item" role="option" on-tap="onEditTap_">
-            $i18n{onStartupEdit}
-          </button>
-          <button class="dropdown-item" role="option" id="remove"
-              on-tap="onRemoveTap_">
-            $i18n{onStartupRemove}
-          </button>
-        </dialog>
+      <template is="dom-if" if="[[editable]]">

[dpapad, 2016/11/18 23:46:28]

Can you add a test checking that a non editable entry does not display the
paper-icon-button?

[Dan Beam, 2016/11/18 23:51:04]

yes (this is exactly the thing I planned on testing, actually)

+        <paper-icon-button id="dots" icon="cr:more-vert"
+            tabindex$="[[tabindex]]" on-tap="onDotsTap_">
+        </paper-icon-button>
+        <template is="cr-lazy-render" id="menu">
+          <dialog is="cr-action-menu">
+            <button class="dropdown-item" role="option" on-tap="onEditTap_">
+              $i18n{onStartupEdit}
+            </button>
+            <button class="dropdown-item" role="option" id="remove"
+                on-tap="onRemoveTap_">
+              $i18n{onStartupRemove}
+            </button>
+          </dialog>
+        </template>
       </template>
     </div>
   </template>
   <script src="startup_url_entry.js"></script>
 </dom-module>