MD Settings: don't allow supervised users to switch to GTK+ theme

chrome/browser/resources/settings/appearance_page/appearance_page.html

 <link rel="import" href="chrome://resources/html/i18n_behavior.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="/appearance_page/appearance_browser_proxy.html">
 <link rel="import" href="/controls/controlled_radio_button.html">
 <link rel="import" href="/controls/settings_dropdown_menu.html">
 <link rel="import" href="/controls/settings_input.html">
@@ skipping 49 matching lines @@
           <template is="dom-if" if="[[prefs.extensions.theme.id.value]]">
             <div class="secondary-action">
               <paper-button id="useDefault" on-tap="onUseDefaultTap_"
                   class="secondary-button">
                 $i18n{resetToDefaultTheme}
               </paper-button>
             </div>
           </template>
 </if>
 <if expr="is_linux and not chromeos">
-          <div class="secondary-action">
-            <template is="dom-if" if="[[showUseClassic_(
-                prefs.extensions.theme.id.value, useSystemTheme_)]]" restamp>
-              <paper-button id="useDefault" on-tap="onUseDefaultTap_"
-                  class="secondary-button">
-                $i18n{useClassicTheme}
-              </paper-button>
-            </template>
-            <template is="dom-if" if="[[showUseSystem_(
-                prefs.extensions.theme.id.value, useSystemTheme_)]]" restamp>
-              <paper-button id="useSystem" on-tap="onUseSystemTap_"
-                  class="secondary-button">
-                $i18n{useSystemTheme}
-              </paper-button>
-            </template>
-          </div>
+          <template is="dom-if" if="[[showThemesSecondary_(
+              prefs.extensions.theme.id.value, useSystemTheme_)]]">
+            <div class="secondary-action">

[dpapad, 2016/10/18 17:49:34]

Can we just make this div hidden instead of wrapping the entire div with a new
dom-if? Performance wise, this will be an empty <div> when hidden, so not a big
deal.

[Dan Beam, 2016/10/18 18:59:52]

Done.

+              <template is="dom-if" if="[[showUseClassic_(
+                  prefs.extensions.theme.id.value, useSystemTheme_)]]" restamp>
+                <paper-button id="useDefault" on-tap="onUseDefaultTap_"
+                    class="secondary-button">
+                  $i18n{useClassicTheme}
+                </paper-button>
+              </template>
+              <template is="dom-if" if="[[showUseSystem_(

[dpapad, 2016/10/18 17:49:34]

Can we add a test regarding showing/hiding the theme buttons based on policy (or
anything else that shows/hides those buttons)?

[Dan Beam, 2016/10/18 18:59:52]

Done.

+                  prefs.extensions.theme.id.value, useSystemTheme_)]]" restamp>
+                <paper-button id="useSystem" on-tap="onUseSystemTap_"
+                    class="secondary-button">
+                  $i18n{useSystemTheme}
+                </paper-button>
+              </template>
+            </div>
+          </template>
 </if>
         </div>
         <div class="settings-box"
             hidden="[[!pageVisibility.homeButton]]">
           <settings-checkbox class="start" label="$i18n{showHomeButton}"
               sub-label="[[getShowHomeSubLabel_(prefs.homepage_is_newtabpage.value, prefs.homepage.value)]]"
               pref="{{prefs.browser.show_home_button}}">
           </settings-checkbox>
         </div>
         <template is="dom-if" if="[[prefs.browser.show_home_button.value]]">
@@ skipping 67 matching lines @@
             associated-control="[[$$('#customize-fonts-subpage-trigger')]]"
             page-title="$i18n{customizeFonts}">
           <settings-appearance-fonts-page prefs="{{prefs}}">
           </settings-appearance-fonts-page>
         </settings-subpage>
       </template>
     </settings-animated-pages>
   </template>
   <script src="appearance_page.js"></script>
 </dom-module>