[NTP] Wait for chromium logo loaded before adjusting width

The logoImg.complete event was not working as intended on Mac's chromium
chrome://apps. Directly using onload event to adjust the width for the
footer menu and the logo instead.

Screencast:
https://screencast.googleplex.com/cast/NTY2NzA1MTk2ODM5NzMxMnw1ZDVjMjU5NS1jYQ

Bug: 864267
Change-Id: I614d44c9377e276f6d3084c299ab9ced98ed831d
Reviewed-on: https://chromium-review.googlesource.com/c/1257676Reviewed-by: Tommy Li <tommycli@chromium.org>
Commit-Queue: Weilun Shi <sweilun@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596368}

chrome/browser/resources/ntp4/new_tab.js

@@ -221,14 +221,16 @@ cr.define('ntp', function() {
    */
   function layoutFooter() {
     // We need the image to be loaded.
-    var logo = $('logo-img');
-    var logoImg = logo.querySelector('img');
-    if (!logoImg.complete) {
+    let logo = $('logo-img');
+    let logoImg = logo.querySelector('img');
+
+    // Only compare the width after the footer image successfully loaded.
+    if (!logoImg.complete || logoImg.width === 0) {
       logoImg.onload = layoutFooter;
       return;
     }
 
-    var menu = $('footer-menu-container');
+    let menu = $('footer-menu-container');
     if (menu.clientWidth > logoImg.width)
       logo.style.WebkitFlex = '0 1 ' + menu.clientWidth + 'px';
     else