[NTP] Add fakebox hover state and transition

Bug: 859381
Cq-Include-Trybots: luci.chromium.try:closure_compilation
Change-Id: Ibd5a7f08e9aa20682ca2a43baf491bcfa43f2ca7
Reviewed-on: https://chromium-review.googlesource.com/1123034Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572494}

chrome/browser/resources/local_ntp/local_ntp.css

@@ -297,6 +297,11 @@ body.alternate-logo #logo-non-white {
   box-shadow: none;
   margin: 0 auto;
   max-width: 560px;
+  transition: background-color 300ms ease-in-out;
+}
+
+.md #fakebox:hover {
+  background-color: rgb(232, 234, 237);
 }
 
 .non-google-page #fakebox-container {