[NTP] Change custom bg attribution to an <a href...> tag

This gives the attribution link the proper context menu.

Screencast: http://go/scrcast/NTkxNDI0NDY2MDg1NDc4NHwyOGZhZTViMy1jMQ

Bug: 963399
Change-Id: Iadccc1a9457b3c7ac6f1093197c937190815821b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1616998Reviewed-by: Gayane Petrosyan <gayane@chromium.org>
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661054}

chrome/browser/resources/local_ntp/custom_backgrounds.js

@@ -241,10 +241,10 @@ customBackgrounds.setMenuVisibility = function() {
 customBackgrounds.setAttribution = function(
     attributionLine1, attributionLine2, attributionActionUrl) {
   const attributionBox = $(customBackgrounds.IDS.ATTRIBUTIONS);
-  const attr1 = document.createElement('div');
-  attr1.setAttribute('id', customBackgrounds.IDS.ATTR1);
-  const attr2 = document.createElement('div');
-  attr2.setAttribute('id', customBackgrounds.IDS.ATTR2);
+  const attr1 = document.createElement('span');
+  attr1.id = customBackgrounds.IDS.ATTR1;
+  const attr2 = document.createElement('span');
+  attr2.id = customBackgrounds.IDS.ATTR2;
 
   if (attributionLine1 !== '') {
     // Shouldn't be changed from textContent for security assurances.
@@ -272,8 +272,8 @@ customBackgrounds.setAttribution = function(
     attr.insertBefore(linkIcon, attr.firstChild);
 
     attributionBox.classList.add(customBackgrounds.CLASSES.ATTR_LINK);
+    attributionBox.href = attributionActionUrl;
     attributionBox.onclick = function() {
-      window.open(attributionActionUrl, '_blank');
       ntpApiHandle.logEvent(
           BACKGROUND_CUSTOMIZATION_LOG_TYPE.NTP_CUSTOMIZE_ATTRIBUTION_CLICKED);
     };
@@ -283,6 +283,9 @@ customBackgrounds.setAttribution = function(
 
 customBackgrounds.clearAttribution = function() {
   const attributions = $(customBackgrounds.IDS.ATTRIBUTIONS);
+  attributions.removeAttribute('href');
+  attributions.className = '';
+  attributions.style.cursor = 'none';
   while (attributions.firstChild) {
     attributions.removeChild(attributions.firstChild);
   }

chrome/browser/resources/local_ntp/local_ntp.html

@@ -109,7 +109,7 @@
       <span id="edit-bg-text"></span>
     </div>
 
-    <div id="custom-bg-attr"></div>
+    <a id="custom-bg-attr"></a>
   </div>
 
   <dialog div id="edit-bg-dialog">

chrome/test/data/local_ntp/local_ntp_browsertest.html

@@ -95,7 +95,7 @@
         <span id="edit-bg-text"></span>
       </div>
 
-      <div id="custom-bg-attr"></div>
+      <a id="custom-bg-attr"></a>
     </div>
 
     <dialog div id="edit-bg-dialog" class="customize-dialog">