cros eula: Focus "close" button for the additional terms dialog

Fixed: 1062246
Change-Id: I04a2c875497b14b5e9418bdd6a2abebabccbc384
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2316205
Auto-Submit: Roman Sorokin [CET] <rsorokin@chromium.org>
Reviewed-by: Renato Silva <rrsilva@google.com>
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791492}

chrome/browser/resources/chromeos/login/oobe_eula.js

@@ -162,6 +162,7 @@ Polymer({
   onAdditionalTermsClicked_() {
     chrome.send('login.EulaScreen.userActed', ['show-additional-tos']);
     this.$['additional-tos'].showModal();
+    this.$['close-additional-tos'].focus();
   },
 
   /**