Downloads: touch up focus equivalents when buttons disappear

This happens when you cancel or retry downloads.

R=aee@chromium.org
BUG=922014

Change-Id: I7639a255911bb88c6c472a19157ce1fe4ceef5ec
Reviewed-on: https://chromium-review.googlesource.com/c/1437545Reviewed-by: Esmael El-Moslimany <aee@chromium.org>
Commit-Queue: Dan Beam (slow until 1/29) <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#626767}

chrome/browser/resources/downloads/item.js

@@ -10,6 +10,9 @@ cr.define('downloads', function() {
       cr.ui.FocusRowBehavior,
     ],
 
+    /** Used by FocusRowBehavior. */
+    overrideCustomEquivalent: true,
+
     properties: {
       /** @type {!downloads.Data} */
       data: Object,
@@ -104,6 +107,17 @@ cr.define('downloads', function() {
       this.content = this.$.content;
     },
 
+    /** Overrides FocusRowBehavior. */
+    getCustomEquivalent: function(sampleElement) {
+      if (sampleElement.getAttribute('focus-type') == 'cancel') {
+        return this.$$('[focus-type="retry"]');
+      }
+      if (sampleElement.getAttribute('focus-type') == 'retry') {
+        return this.$$('[focus-type="pauseOrResume"]');
+      }
+      return null;
+    },
+
     /** @return {!HTMLElement} */
     getFileIcon: function() {
       return assert(this.$['file-icon']);