Enable a11y audits and fix issues for downloads page.

chrome/browser/resources/downloads/downloads.js

Index: chrome/browser/resources/downloads/downloads.js
diff --git a/chrome/browser/resources/downloads/downloads.js b/chrome/browser/resources/downloads/downloads.js
index 34790f849bf4a5bd1370e45ed036a32778a130d8..75124aa47ab415e6fcd7675f7ce5306c2bccdac8 100644
--- a/chrome/browser/resources/downloads/downloads.js
+++ b/chrome/browser/resources/downloads/downloads.js
@@ -323,6 +323,7 @@ function Download(download) {
   }
 
   this.nodeImg_ = createElementWithClassName('img', 'icon');
+  this.nodeImg_.alt = '';
   this.safe_.appendChild(this.nodeImg_);
 
   // FileLink is used for completed downloads, otherwise we show FileName.
@@ -405,6 +406,7 @@ function Download(download) {
   this.node.appendChild(this.danger_);
 
   this.dangerNodeImg_ = createElementWithClassName('img', 'icon');
+  this.dangerNodeImg_.alt = '';
   this.danger_.appendChild(this.dangerNodeImg_);
 
   this.dangerDesc_ = document.createElement('div');