MD Settings: add "Use system title bar and borders"

chrome/browser/resources/options/browser_options.html

 <div id="settings" class="page" hidden>
   <header>
     <h1 i18n-content="settingsTitle"></h1>
   </header>
   <include src="automatic_settings_reset_banner.html">
 <if expr="chromeos">
   <link rel="import" href="chrome://resources/cr_elements/network/cr_network_icon.html">
   <link rel="import" href="chrome://resources/cr_elements/network/cr_onc_types.html">
   <include src="secondary_user_banner.html">
   <section id="network-section-cros">
@@ skipping 74 matching lines @@
         <input type="checkbox"
             pref="bookmark_bar.show_on_all_tabs"
             metric="Options_ShowBookmarksBar">
         <span>
           <span i18n-content="toolbarShowBookmarksBar"></span>
           <span class="controlled-setting-indicator"
               pref="bookmark_bar.show_on_all_tabs"></span>
         </span>
       </label>
     </div>
-<if expr="is_posix and not chromeos and not is_macosx">
+<if expr="is_linux and not chromeos">
     <div class="checkbox"><label>
         <input id="show-window-decorations" type="checkbox"
             pref="browser.custom_chrome_frame" metric="Options_CustomFrame"
             inverted_pref>
         <span i18n-content="showWindowDecorations"></span>
     </label></div>
 </if>
   </section>
 <if expr="chromeos">
   <section id="device-section">
@@ skipping 1019 matching lines @@
       </button>
     </div>
   </section>
   </div>  <!-- advanced-settings-container -->
   </div>  <!-- advanced-settings -->
   <footer id="advanced-settings-footer">
     <a is="action-link" id="advanced-settings-expander"
         i18n-content="showAdvancedSettings"></a>
   </footer>
 </div>