ntp: add tooltips for all tile types

chrome/browser/resources/ntp4/most_visited_page.js

Index: chrome/browser/resources/ntp4/most_visited_page.js
diff --git a/chrome/browser/resources/ntp4/most_visited_page.js b/chrome/browser/resources/ntp4/most_visited_page.js
index 794abe2ab1f41c1cdd42cf6856f9319808e4fe21..621dfba7b43a273a2f9ae44a024d9c9954891857 100644
--- a/chrome/browser/resources/ntp4/most_visited_page.js
+++ b/chrome/browser/resources/ntp4/most_visited_page.js
@@ -64,6 +64,7 @@ cr.define('ntp4', function() {
       this.removeAttribute('tabIndex');
       this.data_ = null;
       this.removeAttribute('id');
+      this.title = '';
     },
 
     /**
@@ -103,6 +104,9 @@ cr.define('ntp4', function() {
       title.textContent = data.title;
       title.dir = data.direction;
 
+      // Sets the tooltip.
+      this.title = data.title;
+
       var thumbnailUrl = data.thumbnailUrl || 'chrome://thumb/' + data.url;
       this.querySelector('.thumbnail').style.backgroundImage =
           url(thumbnailUrl);