Add ARC version to help and version pages

components/version_ui/resources/about_version.js

Index: components/version_ui/resources/about_version.js
diff --git a/components/version_ui/resources/about_version.js b/components/version_ui/resources/about_version.js
index 476311bfae9837eed6419c27409ddf6eab078d8a..c335b6360cd8f58fdfb33b187ceea223db923bc0 100644
--- a/components/version_ui/resources/about_version.js
+++ b/components/version_ui/resources/about_version.js
@@ -40,9 +40,20 @@ function returnOsVersion(osVersion) {
   $('os_version').textContent = osVersion;
 }
 
+
+/**
+ * Callback from the backend with the ARC version to display.
+ * @param {string} arcVersion The ARC version to display.
+ */
+function returnARCVersion(arcVersion) {
+  $('arc_version').textContent = arcVersion;
+  $('arc_holder').hidden = !arcVersion;
+}
+
 /* All the work we do onload. */
 function onLoadWork() {
   chrome.send('requestVersionInfo');
+  $('arc_holder').hidden = true;
 }
 
 document.addEventListener('DOMContentLoaded', onLoadWork);