[MD settings] tweaks to what is shown in about page; and css cleanup

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

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="/controls/settings_checkbox.html">
 <link rel="import" href="/i18n_setup.html">
 <link rel="import" href="/route.html">
 <link rel="import" href="/settings_shared_css.html">
 <link rel="import" href="/settings_vars_css.html">
 
 <dom-module id="settings-manage-a11y-page">
   <template>
     <style include="settings-shared">
       .indented {
         -webkit-margin-start: 20px;
       }
 
       .no-top-border {
         border-top: none;
       }
 
-      .settings-box iron-icon {
-        -webkit-margin-end: var(--iron-icon-spacing);
-      }
-
       .settings-box settings-checkbox {
         flex-grow: 1;
       }
 
       .list-item settings-dropdown-menu {
         -webkit-margin-start: 16px;
       }
     </style>
     <div class="settings-box row first">
       <span>
@@ skipping 27 matching lines @@
         <settings-checkbox label="$i18n{highContrastLabel}"
             pref="{{prefs.settings.a11y.high_contrast_enabled}}">
         </settings-checkbox>
         <settings-checkbox label="$i18n{screenMagnifierLabel}"
             pref="{{prefs.settings.a11y.screen_magnifier}}">
         </settings-checkbox>
       </div>
       <div class="settings-box two-line indented" on-tap="onDisplayTap_"
           actionable>
         <iron-icon icon="settings:desktop-windows"></iron-icon>
-        <div class="start">
+        <div class="middle">
           <div>$i18n{displaySettingsTitle}</div>
           <div class="secondary">$i18n{displaySettingsDescription}</div>
         </div>
       </div>
       <div class="settings-box two-line indented" on-tap="onAppearanceTap_"
           actionable>
         <iron-icon icon="settings:text-format"></iron-icon>
-        <div class="start">
+        <div class="middle">
           <div>$i18n{appearanceSettingsTitle}</div>
           <div class="secondary">$i18n{appearanceSettingsDescription}</div>
         </div>
       </div>
 
       <h2>$i18n{keyboardHeading}</h2>
       <div class="settings-box block first indented">
         <settings-checkbox
             pref="{{prefs.settings.a11y.sticky_keys_enabled}}"
             label="$i18n{stickyKeysLabel}">
         </settings-checkbox>
         <settings-checkbox pref="{{prefs.settings.a11y.virtual_keyboard}}"
             label="$i18n{onScreenKeyboardLabel}">
         </settings-checkbox>
         <settings-checkbox pref="{{prefs.settings.a11y.focus_highlight}}"
             label="$i18n{focusHighlightLabel}">
         </settings-checkbox>
         <settings-checkbox pref="{{prefs.settings.a11y.caret_highlight}}"
             label="$i18n{caretHighlightLabel}">
         </settings-checkbox>
         <template is="dom-if" if="[[showExperimentalFeatures_]]">
           <settings-checkbox pref="{{prefs.settings.a11y.switch_access}}"
               label="$i18n{switchAccessLabel}">
           </settings-checkbox>
         </template>
       </div>
       <div class="settings-box two-line indented" on-tap="onKeyboardTap_"
           actionable>
         <iron-icon icon="settings:keyboard"></iron-icon>
-        <div class="start">
+        <div class="middle">
           <div>$i18n{keyboardSettingsTitle}</div>
           <div class="secondary">$i18n{keyboardSettingsDescription}</div>
         </div>
       </div>
 
       <h2>$i18n{mouseAndTouchpadHeading}</h2>
       <div class="settings-box block first indented">
         <settings-checkbox label="$i18n{clickOnStopLabel}"
             pref="{{prefs.settings.a11y.autoclick}}">
         </settings-checkbox>
@@ skipping 10 matching lines @@
         <settings-checkbox label="$i18n{largeMouseCursorLabel}"
             pref="{{prefs.settings.a11y.large_cursor_enabled}}">
         </settings-checkbox>
         <settings-checkbox pref="{{prefs.settings.a11y.cursor_highlight}}"
             label="$i18n{cursorHighlightLabel}">
         </settings-checkbox>
       </div>
       <div class="settings-box two-line indented" on-tap="onMouseTap_"
           actionable>
         <iron-icon icon="settings:mouse"></iron-icon>
-        <div class="start">
+        <div class="middle">
           <div>$i18n{mouseSettingsTitle}</div>
           <div class="secondary">$i18n{mouseSettingsDescription}</div>
           <button class="icon-arrow-right" is="paper-icon-button-light">
           </button>
         </div>
       </div>
 
       <h2>$i18n{audioHeading}</h2>
       <div class="settings-box block first indented">
         <settings-checkbox pref="{{prefs.settings.a11y.mono_audio}}"
             label="$i18n{monoAudioLabel}">
         </settings-checkbox>
       </div>
     </div>
 
     <div class="settings-box two-line" on-tap="onMoreFeaturesTap_" actionable>
       <div class="start">
         <div>$i18n{additionalFeaturesTitle}</div>
         <div class="secondary">$i18n{a11yWebStore}</div>
       </div>
       <button class="icon-external" is="paper-icon-button-light"></button>
     </div>
   </template>
   <script src="manage_a11y_page.js"></script>
 </dom-module>