MD Settings: Restore focus after closing various dialogs.

chrome/browser/resources/settings/reset_page/reset_page.html

 <link rel="import" href="chrome://resources/cr_elements/cr_lazy_render/cr_lazy_render.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="../i18n_setup.html">
 <link rel="import" href="reset_profile_dialog.html">
 <link rel="import" href="../route.html">
 <link rel="import" href="../settings_shared_css.html">
 
 <if expr="chromeos">
 <link rel="import" href="powerwash_dialog.html">
 </if>
 
 <dom-module id="settings-reset-page">
   <template>
     <style include="settings-shared"></style>
     <div class="settings-box first two-line" id="resetProfile"
         on-tap="onShowResetProfileDialog_" actionable>
       <div class="start">
         $i18n{resetPageTitle}
         <div class="secondary" id="resetProfileSecondary">
           $i18n{resetPageDescription}
         </div>
       </div>
-      <button class="subpage-arrow" is="paper-icon-button-light"
-          aria-label="$i18n{resetPageTitle}"
+      <button id="resetProfileArrow" is="paper-icon-button-light"
+          class="subpage-arrow" aria-label="$i18n{resetPageTitle}"
           aria-describedby="resetProfileSecondary"></button>
     </div>
     <template is="dom-if" if="[[showResetProfileDialog_]]" restamp>
       <settings-reset-profile-dialog on-close="onResetProfileDialogClose_">
       </settings-reset-profile-dialog>
     </template>
 <if expr="chromeos">
     <div class="settings-box two-line" id="powerwash" actionable
         on-tap="onShowPowerwashDialog_" hidden="[[!allowPowerwash_]]">
       <div class="start">
         $i18n{powerwashTitle}
         <div class="secondary" id="powerwashSecondary">
           $i18n{powerwashDescription}
         </div>
       </div>
-      <button class="subpage-arrow" is="paper-icon-button-light"
-          aria-label="$i18n{powerwashTitle}"
+      <button id="powerwashArrow" is="paper-icon-button-light"
+          class="subpage-arrow" aria-label="$i18n{powerwashTitle}"
           aria-describedby="powerwashSecondary"></button>
     </div>
     <template is="dom-if" if="[[showPowerwashDialog_]]" restamp>
       <settings-powerwash-dialog on-close="onPowerwashDialogClose_">
       </settings-powerwash-dialog>
     </template>
 </if>
   </template>
   <script src="reset_page.js"></script>
 </dom-module>