Enable a11y audit for chrome://print and fix failing tests.

chrome/browser/resources/print_preview/previewarea/preview_area.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.
 
 /**
  * @typedef {{accessibility: Function,
  *            documentLoadComplete: Function,
  *            getHeight: Function,
  *            getHorizontalScrollbarThickness: Function,
  *            getPageLocationNormalized: Function,
@@ skipping 181 matching lines @@
   PreviewArea.Classes_ = {
     COMPATIBILITY_OBJECT: 'preview-area-compatibility-object',
     OUT_OF_PROCESS_COMPATIBILITY_OBJECT:
         'preview-area-compatibility-object-out-of-process',
     CUSTOM_MESSAGE_TEXT: 'preview-area-custom-message-text',
     MESSAGE: 'preview-area-message',
     INVISIBLE: 'invisible',
     OPEN_SYSTEM_DIALOG_BUTTON: 'preview-area-open-system-dialog-button',
     OPEN_SYSTEM_DIALOG_BUTTON_THROBBER:
         'preview-area-open-system-dialog-button-throbber',
-    OVERLAY: 'preview-area-overlay-layer'
+    OVERLAY: 'preview-area-overlay-layer',
+    OVERLAYED: 'preview-area-overlayed',
+    MARGIN_CONTROL: 'margin-control',
+    PREVIEW_AREA: 'preview-area-plugin-wrapper'
   };
 
   /**
    * Enumeration of IDs shown in the preview area.
    * @enum {string}
    * @private
    */
   PreviewArea.MessageId_ = {
     CUSTOM: 'custom',
     LOADING: 'loading',
@@ skipping 284 matching lines @@
         var customMessageTextEl = this.getElement().getElementsByClassName(
             PreviewArea.Classes_.CUSTOM_MESSAGE_TEXT)[0];
         customMessageTextEl.textContent = opt_message;
       } else if (messageId == PreviewArea.MessageId_.LOADING) {
         jumpingDotsEl.classList.add('jumping-dots');
       }
       var messageEl = this.getElement().getElementsByClassName(
             PreviewArea.MessageIdClassMap_[messageId])[0];
       setIsVisible(messageEl, true);
 
-      // Show overlay.
-      this.overlayEl_.classList.remove(PreviewArea.Classes_.INVISIBLE);
+      this.showOverlay_();
     },
 
     /**
+     * Shows the message overlay.
+     * @private
+     */
+    showOverlay_: function() {
+      this.overlayEl_.classList.remove(PreviewArea.Classes_.INVISIBLE);
+
+      // Hide all controls that will be hidden when the overlay is visible.
+      var marginControls = this.getElement().getElementsByClassName(
+          PreviewArea.Classes_.MARGIN_CONTROL);
+      for (var i = 0; i < marginControls.length; ++i) {
+        marginControls[i].classList.add(PreviewArea.Classes_.OVERLAYED);
+      }
+      var previewAreaControls = this.getElement().getElementsByClassName(
+          PreviewArea.Classes_.PREVIEW_AREA);
+      for (var i = 0; i < previewAreaControls.length; ++i) {
+        previewAreaControls[i].classList.add(PreviewArea.Classes_.OVERLAYED);
+      }
+    },
+
+    /**
      * Hides the message overlay.
      * @private
      */
     hideOverlay_: function() {
       this.overlayEl_.classList.add(PreviewArea.Classes_.INVISIBLE);
+
+      // Display all controls that will be visible when the overlay is no longer
+      // visible.
+      var marginControls = this.getElement().getElementsByClassName(
+          PreviewArea.Classes_.MARGIN_CONTROL);
+      for (var i = 0; i < marginControls.length; ++i) {
+        marginControls[i].classList.remove(PreviewArea.Classes_.OVERLAYED);
+      }
+      var previewAreaControls = this.getElement().getElementsByClassName(
+          PreviewArea.Classes_.PREVIEW_AREA);
+      for (var i = 0; i < previewAreaControls.length; ++i) {
+        previewAreaControls[i].classList.remove(PreviewArea.Classes_.OVERLAYED);
+      }
+
       // Disable jumping animation to conserve cycles.
       var jumpingDotsEl = this.getElement().querySelector(
           '.preview-area-loading-message-jumping-dots');
       jumpingDotsEl.classList.remove('jumping-dots');
     },
 
     /**
      * Creates a preview plugin and adds it to the DOM.
      * @param {string} srcUrl Initial URL of the plugin.
      * @private
@@ skipping 244 matching lines @@
             new print_preview.Size(viewportWidth, viewportHeight));
       }
     }
   };
 
   // Export
   return {
     PreviewArea: PreviewArea
   };
 });