Enable a11y audits and fix issues for downloads page.

chrome/browser/resources/downloads/downloads.js

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // TODO(jhawkins): Use hidden instead of showInline* and display:none.
 
 /**
  * The type of the download object. The definition is based on
  * chrome/browser/ui/webui/downloads_dom_handler.cc:CreateDownloadItemValue()
  * @typedef {{by_ext_id: (string|undefined),
@@ skipping 305 matching lines @@
     this.nodeProgressForeground_ =
         createElementWithClassName('canvas', 'progress');
     this.nodeProgressForeground_.width = Download.Progress.width;
     this.nodeProgressForeground_.height = Download.Progress.height;
     this.canvasProgress_ = this.nodeProgressForeground_.getContext('2d');
 
     this.safe_.appendChild(this.nodeProgressForeground_);
   }
 
   this.nodeImg_ = createElementWithClassName('img', 'icon');
+  this.nodeImg_.alt = '';
   this.safe_.appendChild(this.nodeImg_);
 
   // FileLink is used for completed downloads, otherwise we show FileName.
   this.nodeTitleArea_ = createElementWithClassName('div', 'title-area');
   this.safe_.appendChild(this.nodeTitleArea_);
 
   this.nodeFileLink_ = createLink(this.openFile_.bind(this), '');
   this.nodeFileLink_.className = 'name';
   this.nodeFileLink_.style.display = 'none';
   this.nodeTitleArea_.appendChild(this.nodeFileLink_);
@@ skipping 62 matching lines @@
   this.nodeControls_.appendChild(this.controlCancel_);
 
   this.controlByExtension_ = document.createElement('span');
   this.nodeControls_.appendChild(this.controlByExtension_);
 
   // Container for 'unsafe download' UI.
   this.danger_ = createElementWithClassName('div', 'show-dangerous');
   this.node.appendChild(this.danger_);
 
   this.dangerNodeImg_ = createElementWithClassName('img', 'icon');
+  this.dangerNodeImg_.alt = '';
   this.danger_.appendChild(this.dangerNodeImg_);
 
   this.dangerDesc_ = document.createElement('div');
   this.danger_.appendChild(this.dangerDesc_);
 
   // Buttons for the malicious case.
   this.malwareNodeControls_ = createElementWithClassName('div', 'controls');
   this.malwareSave_ = createLink(
       this.saveDangerous_.bind(this),
       loadTimeData.getString('danger_restore'));
@@ skipping 564 matching lines @@
       resultsTimeout = setTimeout(tryDownloadUpdatedPeriodically, 5);
       break;
     }
   }
 }
 
 // Add handlers to HTML elements.
 window.addEventListener('DOMContentLoaded', load);
 
 preventDefaultOnPoundLinkClicks();  // From util.js.