[profiles] Remove voiceover for avatar URLs

The avatar images in profile UIs did not have any accessibility options,
and the voice over was spelling out the whole image URL, which is a
broken experience.
The voice over label for the avatars is not strictly required, and thus
this CL disables the voice over by passing an empty 'alt' attribute to
the images.

Fixed: 1151916
Change-Id: Ifd098e78842a3b01e1bd28d19baf8e2aac86c4d7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2565432
Auto-Submit: David Roger <droger@chromium.org>
Commit-Queue: Esmael Elmoslimany <aee@chromium.org>
Reviewed-by: Esmael Elmoslimany <aee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832032}

chrome/browser/resources/signin/dice_web_signin_intercept/dice_web_signin_intercept_app.html

@@ -112,7 +112,7 @@
 <div id="header">
   <div id="headerText">[[interceptionParameters_.headerText]]</div>
   <div id="avatar-container">
-    <img id="avatar"
+    <img id="avatar" alt=""
         src="[[interceptionParameters_.interceptedAccount.pictureUrl]]">
     <div class="work-badge" id="badge"
         hidden="[[!interceptionParameters_.interceptedAccount.isManaged]]">

chrome/browser/resources/signin/profile_customization/profile_customization_app.html

@@ -121,7 +121,7 @@
 <div id="header">
   <div id="headerText">[[initialProfileName_]]</div>
   <div id="avatarContainer">
-    <img id="avatar" src="[[pictureUrl_]]">
+    <img id="avatar" alt="" src="[[pictureUrl_]]">
     <div class="work-badge" id="badge" hidden="[[!isManaged_]]">
       <iron-icon class="icon" icon="cr:domain"></iron-icon>
     </div>

chrome/browser/resources/signin/profile_picker/profile_creation_flow/local_profile_customization.html

@@ -121,7 +121,7 @@
         on-click="onClickBack_" aria-label="$i18n{backButtonLabel}">
   </cr-icon-button>
   <h2 id="title">$i18n{localProfileCreationTitle}</h2>
-  <img class="avatar" src$="[[profileThemeInfo.themeGenericAvatar]]">
+  <img class="avatar" alt="" src$="[[profileThemeInfo.themeGenericAvatar]]">
 </div>
 
 <div id="wrapperContainer">

chrome/browser/resources/signin/profile_picker/profile_creation_flow/profile_type_choice.html

@@ -55,7 +55,7 @@
       disabled="[[loadSigninInProgess_]]">
   </cr-icon-button>
   <div id="signinPromoBanner" class="banner"></div>
-  <img class="avatar" src="[[profileThemeInfo.themeGenericAvatar]]">
+  <img class="avatar" alt="" src="[[profileThemeInfo.themeGenericAvatar]]">
 </div>
 <div class="title-container">
   <h2>$i18n{profileTypeChoiceTitle}</h2>