webui: fix up chrome://settings/passwords a11y

This change:
1) Removes the title from the group containing the site's name.
   Before this change, that group would have read as:
     group, one item, https://the.full.hostname.here..., displayed.hostname
   After this change, it reads as:
     link, displayed.hostname
2) Adds an ARIA label for the username field, which is otherwise read
   as the username text without context
3) ARIA-hides the table headers, since the corresponding cells of the
   table are now either self-explanatory or labelled

Bug: 956434
Change-Id: If9dc5b5ccac83adf3375feb461fce0f0299172d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829777Reviewed-by: Hector Carmona <hcarmona@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702136}

chrome/browser/resources/settings/autofill_page/password_list_item.html

@@ -50,8 +50,7 @@
       }
     </style>
     <div class="list-item" focus-row-container>
-      <div class="website-column no-min-width"
-          title="[[item.entry.urls.link]]">
+      <div class="website-column no-min-width">
         <site-favicon url="[[item.entry.urls.link]]"></site-favicon>
         <a id="originUrl" target="_blank" class="no-min-width"
             href="[[item.entry.urls.link]]"
@@ -64,14 +63,17 @@
         </a>
       </div>
       <input id="username" class="username-column password-field"
-          readonly tabindex="-1" value="[[item.entry.username]]">
+          aria-label="$i18n{editPasswordUsernameLabel}"
+          readonly value="[[item.entry.username]]"
+          focus-row-control focus-type="username">
       <div class="password-column">
         <template is="dom-if" if="[[!item.entry.federationText]]">
           <input id="password" aria-label=$i18n{editPasswordPasswordLabel}
               type="[[getPasswordInputType_(item.password)]]"
               on-click="onReadonlyInputTap_" class="password-field" readonly
               disabled$="[[!item.password]]"
-              value="[[getPassword_(item.password)]]">
+              value="[[getPassword_(item.password)]]"
+              focus-row-control focus-type="passwordField">
           <cr-icon-button id="showPasswordButton"
               class$="[[getIconClass_(item.password)]]"
               on-click="onShowPasswordButtonTap_"

chrome/browser/resources/settings/autofill_page/passwords_section.html

@@ -110,7 +110,8 @@
     </div>
     <div class="list-frame">
       <div id="savedPasswordsHeaders" class="list-item column-header"
-          hidden$="[[!hasSome_(savedPasswords, savedPasswords.splices)]]">
+          hidden$="[[!hasSome_(savedPasswords, savedPasswords.splices)]]"
+          aria-hidden="true">
         <div class="website-column">$i18n{editPasswordWebsiteLabel}</div>
         <div class="username-column">
           $i18n{editPasswordUsernameLabel}