MD Settings: Fix case where "Check for updates" is accidentally shown.

chrome/browser/resources/settings/about_page/about_page.js

Index: chrome/browser/resources/settings/about_page/about_page.js
diff --git a/chrome/browser/resources/settings/about_page/about_page.js b/chrome/browser/resources/settings/about_page/about_page.js
index ef1eb16d17ba384209ecc1474744935e3b1b93d9..1e53ea6d7c58bbafc7b964ee3d70570a14eb1a22 100644
--- a/chrome/browser/resources/settings/about_page/about_page.js
+++ b/chrome/browser/resources/settings/about_page/about_page.js
@@ -373,8 +373,12 @@ Polymer({
    * @private
    */
   computeShowCheckUpdates_: function() {
-    return !this.hasCheckedForUpdates_ ||
-        this.checkStatus_(UpdateStatus.FAILED);
+    // Enable the update button if we are in a stale 'updated' status or
+    // update has failed. Disable it otherwise.
+    var staleUpdatedStatus = !this.hasCheckedForUpdates_ &&
+        this.checkStatus_(UpdateStatus.UPDATED);
+
+    return staleUpdatedStatus || this.checkStatus_(UpdateStatus.FAILED);
   },
 
   /**