ntp4: polish app trashing

chrome/browser/resources/ntp4/tile_page.css

Index: chrome/browser/resources/ntp4/tile_page.css
diff --git a/chrome/browser/resources/ntp4/tile_page.css b/chrome/browser/resources/ntp4/tile_page.css
index 37d989777d593ea1ed148b5f2806732df37f39ec..4b1c87fe24bad217a527e27b4f9f6ac8419a3a4e 100644
--- a/chrome/browser/resources/ntp4/tile_page.css
+++ b/chrome/browser/resources/ntp4/tile_page.css
@@ -73,6 +73,7 @@
   pointer-events: none;
   position: fixed;
   z-index: 3;
+  -webkit-transition: opacity 0.2s;
 }
 
 .tile.drag-representation.placing > * {
@@ -89,6 +90,10 @@
   -webkit-transition: left 200ms, right 200ms, top 200ms;
 }
 
+.hovering-on-trash {
+  opacity: 0.6;
+}
+
 .animating-tile-page .top-margin {
   -webkit-transition: margin-bottom 200ms;
 }