A11y: Add the option to always show the a11y tray menu regardless of the state of a11y features

chrome/browser/resources/options/browser_options.html

 <div id="settings" class="page" hidden>
   <header>
     <h1 i18n-content="settingsTitle"></h1>
   </header>
 <if expr="not pp_ifdef('chromeos')">
   <include src="sync_section.html">
 </if>
 <if expr="pp_ifdef('chromeos')">
   <section>
     <h3 i18n-content="sectionTitleInternet"></h3>
@@ skipping 590 matching lines @@
     <h3 i18n-content="accessibilityTitle"></h3>
     <div class="option-control-table">
       <p id="accessibility-explanation" class="settings-row">
         <span i18n-content="accessibilityExplanation"></span>
         <a target="_blank" i18n-content="learnMore"
             i18n-values="href:accessibilityLearnMoreURL"></a>
       </p>
       <div class="option-name">
         <div class="checkbox">
           <label>
+            <input id="accessibility-should-always-show-menu"
+                pref="settings.a11y.enable_menu" type="checkbox">
+            <span i18n-content="accessibilityAlwaysShowMenu"></span>
+          </label>
+        </div>
+      </div>
+      <div class="option-name">
+        <div class="checkbox">
+          <label>
             <input id="accessibility-spoken-feedback-check" type="checkbox">
             <span i18n-content="accessibilitySpokenFeedback"></span>
           </label>
         </div>
       </div>
       <div class="option-name">
         <div class="checkbox">
           <label>
             <input id="accessibility-high-contrast-check" type="checkbox">
             <span i18n-content="accessibilityHighContrast"></span>
@@ skipping 60 matching lines @@
   </section>
 </if>
 </div>  <!-- advanced-settings-container -->
 </div>  <!-- advanced-settings -->
 <footer>
   <button id="advanced-settings-expander" class="link-button"
       i18n-content="showAdvancedSettings">
   </button>
 </footer>
 </div>