[ConsentV2] Fix some a11y issues

This CL fixes below a11y issues:
* Add labels for close buttons of consent message and consent dialog.
* Make some image alternatives null for screen readers.
* Try to grab focus for consent toast when it's shown.
* Try to focus back to cart module when the consent is dismissed.

(cherry picked from commit be921de)

Bug: 1314136
Change-Id: Idcd858dd6ca318268123ed5b0d7b351e268f0ac5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3579820
Reviewed-by: Mei Liang <meiliang@chromium.org>
Reviewed-by: Mohamad Ahmadi <mahmadi@chromium.org>
Commit-Queue: Yue Zhang <yuezhanggg@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#993016}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3600747
Cr-Commit-Position: refs/branch-heads/5005@{#155}
Cr-Branched-From: 5b4d945-refs/heads/main@{#992738}

chrome/browser/resources/new_tab_page/modules/cart/discount_consent_card.html

@@ -97,7 +97,7 @@
           as="merchant">
         <li class="favicon">
           <img class="favicon-image" is="cr-auto-img"
-              auto-src="[[getFaviconUrl_(merchant.cartUrl.url)]]"></img>
+              auto-src="[[getFaviconUrl_(merchant.cartUrl.url)]]" alt=""></img>
         </li>
       </template>
     </ul>
@@ -137,7 +137,7 @@
     </iron-pages>
   </div>
   <template is="dom-if" if="[[showCloseButton_]]" restamp>
-    <cr-icon-button id="close" class="icon-clear"
+    <cr-icon-button id="close" class="icon-clear" aria-label="$i18n{close}"
         on-click="onCloseClick_"></cr-icon-button>
   </template>
 </div>

chrome/browser/resources/new_tab_page/modules/cart/discount_consent_dialog.html

@@ -48,15 +48,15 @@
 </style>
 
 <cr-dialog id="dialog" show-close-button on-cancel="onDismissClick_"
-    show-on-attach>
+    show-on-attach close-text="$i18n{close}">
   <div slot="title">$i18n{modulesCartSentence}</div>
   <div slot="body">
     <div id="content-container">
       <div id="content-title">$i18n{modulesCartDiscountConentTitle}</div>
       <div id="content">$i18n{modulesCartDiscountConsentContentV3}</div>
     </div>
     <div id="icon-container">
-      <img id="icon" src="modules/cart/icons/consent_icon.svg">
+      <img id="icon" src="modules/cart/icons/consent_icon.svg" alt="">
     </div>
   </div>
   <div slot="button-container">

chrome/browser/resources/new_tab_page/modules/cart/module.ts

@@ -410,6 +410,7 @@ export class ChromeCartModuleElement extends I18nMixin
     this.confirmDiscountConsentString_ =
         loadTimeData.getString('modulesCartDiscountConsentRejectConfirmation');
     this.$.confirmDiscountConsentToast.show();
+    this.$.confirmDiscountConsentToast.focus();
     ChromeCartProxy.getHandler().onDiscountConsentAcknowledged(false);
     chrome.metricsPrivate.recordUserAction(
         'NewTabPage.Carts.RejectDiscountConsent');
@@ -420,13 +421,19 @@ export class ChromeCartModuleElement extends I18nMixin
     this.confirmDiscountConsentString_ =
         loadTimeData.getString('modulesCartDiscountConsentAcceptConfirmation');
     this.$.confirmDiscountConsentToast.show();
+    this.$.confirmDiscountConsentToast.focus();
     ChromeCartProxy.getHandler().onDiscountConsentAcknowledged(true);
     chrome.metricsPrivate.recordUserAction(
         'NewTabPage.Carts.AcceptDiscountConsent');
   }
 
   private onDiscountConsentDismissed_() {
     this.showDiscountConsent = false;
+    const firstCart =
+        this.$.cartCarousel.querySelector<HTMLElement>('.cart-container');
+    if (firstCart !== null) {
+      firstCart.focus();
+    }
     ChromeCartProxy.getHandler().onDiscountConsentDismissed();
     chrome.metricsPrivate.recordUserAction(
         'NewTabPage.Carts.DismissDiscountConsent');