[NTP] Show focus outline on selected bg tile

Show the focus outline on a selected bg tile when navigating with the
keyboard.

http://go/scrcast/NTA2NTc0NTg1MzU3OTI2NHw1NGE3MmRmYS02Ng

Bug: 937570
Change-Id: I96c1449ddff90a5c32a2348607506ab5ae728743
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1728045Reviewed-by: Gayane Petrosyan <gayane@chromium.org>
Commit-Queue: Kyle Milka <kmilka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683399}

chrome/browser/resources/local_ntp/local_ntp.css

@@ -952,9 +952,9 @@ html[dir=rtl] .menu-option {
   }
 }
 
-#backgrounds-menu .bg-sel-tile-bg.selected .bg-sel-tile:focus,
-#backgrounds-image-menu .bg-sel-tile-bg.selected .bg-sel-tile:focus {
-  outline: none;
+:not(.using-mouse-nav) :-webkit-any(#backgrounds-menu, #backgrounds-image-menu)
+  .bg-sel-tile-bg.selected:focus-within {
+  outline: auto -webkit-focus-ring-color;
 }
 
 .using-mouse-nav .bg-sel-tile:focus {