Hide a11y fullscreen/docked magnifier zoom levels when disabled

Bug: 1000821
Change-Id: I8f492141e66f2048bfe2edb0daceec6d2214540e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1838232Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Commit-Queue: Gavin Williams <gavinwill@chromium.org>
Cr-Commit-Position: refs/heads/master@{#703773}

chrome/browser/resources/settings/a11y_page/manage_a11y_page.html

@@ -80,6 +80,7 @@
         label="$i18n{screenMagnifierLabel}"
         disabled="[[prefs.ash.docked_magnifier.enabled.value]]">
     </settings-toggle-button>
+    <template is="dom-if" if="[[prefs.settings.a11y.screen_magnifier.value]]">
       <div class="settings-box continuation">
         <div class="start sub-item settings-box-text">
           $i18n{screenMagnifierZoomLabel}
@@ -90,11 +91,13 @@
             disabled="[[!prefs.settings.a11y.screen_magnifier.value]]">
         </settings-dropdown-menu>
       </div>
+    </template>
     <settings-toggle-button
         pref="{{prefs.ash.docked_magnifier.enabled}}"
         label="$i18n{dockedMagnifierLabel}"
         disabled="[[prefs.settings.a11y.screen_magnifier.value]]">
     </settings-toggle-button>
+    <template is="dom-if" if="[[prefs.ash.docked_magnifier.enabled.value]]">
       <div class="settings-box continuation">
         <div class="start sub-item settings-box-text">
           $i18n{dockedMagnifierZoomLabel}
@@ -105,6 +108,7 @@
             disabled="[[!prefs.ash.docked_magnifier.enabled.value]]">
         </settings-dropdown-menu>
       </div>
+    </template>
     <cr-link-row class="hr" label="$i18n{displaySettingsTitle}"
         on-click="onDisplayTap_" sub-label="$i18n{displaySettingsDescription}"
         embedded></cr-link-row>