remove ntp app install hint

chrome/browser/resources/ntp4/apps_page.css

 /* Copyright (c) 2012 The Chromium Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file. */
 
 .app {
   outline: none;
   position: absolute;
   text-align: center;
 }
 
@@ skipping 156 matching lines @@
 
 .app .invisible {
   visibility: hidden;
 }
 
 /* Move the notification lower on apps pages to account for the 16px of
  * transparency each app icon should have. */
 .apps-page #notification-container {
   bottom: 15px;
 }
-
-/* App install hint */
-
-.app-install-hint {
-  -webkit-transition: opacity 150ms;
-  color: inherit;
-  display: block;
-  opacity: 0.8;
-  position: absolute;
-  text-decoration: none;
-}
-
-.app-install-hint:active {
-  opacity: 1.0;
-}
-
-.app-install-hint-interior {
-  border: 2px dashed;
-  border-radius: 20%;
-  box-sizing: border-box;
-  height: 60%;
-  left: 20%;
-  position: absolute;
-  right: 20%;
-  top: 10%;
-  width: 60%;
-}
-
-.app-install-hint-interior > .interior-background {
-  border-radius: 20%;
-  bottom: 3px;
-  left: 3px;
-  position: absolute;
-  right: 3px;
-  top: 3px;
-}
-
-.app-install-hint-interior > .vertical-bar,
-.app-install-hint-interior > .horizontal-bar {
-  border-radius: 2px;
-  position: absolute;
-}
-
-.app-install-hint-interior > .vertical-bar {
-  height: 50%;
-  left: 44%;
-  right: 44%;
-  top: 25%;
-  width: 12%;
-}
-
-.app-install-hint-interior > .horizontal-bar {
-  height: 12%;
-  left: 25%;
-  right: 25%;
-  top: 44%;
-  width: 50%;
-}
-
-html.dragging-mode .app-install-hint {
-  opacity: 0;
-}
-
-.app-install-hint > span {
-  font-size: 1.2em;
-  left: 0;
-  position: absolute;
-  right: 0;
-  top: 80%;
-  white-space: nowrap;
-}