ntp4: increase size of left/right page margins

chrome/browser/resources/ntp4/tile_page.css

 /* Copyright (c) 2011 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.
  */
 
 .tile-page {
   height: 100%;
   position: relative;
   width: 100%;
 }
 
 .tile-page-scrollbar {
   margin: 0 4px;
   pointer-events: none;
   position: absolute;
   right: 0;
   width: 5px;
   z-index: 5;
   -webkit-box-sizing: border-box;
 }
 
 .tile-page-content {
   height: 100%;
   overflow-y: scroll;
   padding-top: 100px;
   position: relative;
   text-align: center;
   width: 100%;
+  /* TODO(estade): this mask is disabled for technical reasons. It negatively
+   * impacts performance of page switching, also it causes problems with Mac
+   * text: http://crbug.com/86955
   -webkit-mask-image: -webkit-linear-gradient(bottom, transparent, black 30px);
+  */
   /* The following four properties are necessary so that the mask won't clip
    * the scrollbar. */
   box-sizing: border-box;
-  /* Scrollbar + balance right padding.  */
-  padding-left: 26px;
-  /* Same width as the scrollbar. */
-  padding-right: 13px;
+  /* Scrollbar width(13px) + balance right padding.  */
+  padding-left: 93px;
+  padding-right: 80px;
   /* Don't apply clip mask to padding. */
   -webkit-mask-clip: content-box;
 }
 
 .tile-grid {
   overflow: hidden;
   position: relative;
   width: 100%;
 }
 
@@ skipping 106 matching lines @@
 
 /** Scrollbars ****************************************************************/
 
 .tile-page-content::-webkit-scrollbar {
   width: 13px;
 }
 
 .tile-page-content::-webkit-scrollbar-button {
   display: none;
 }