[Local NTP] block image-related context menu items for thumbnails; CSS fixes.

chrome/browser/resources/local_ntp/local_ntp.css

 /* Copyright 2013 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. */
 body {
   background-attachment: fixed !important;
   background-color: white;
   cursor: default;
   font-family: arial, sans-serif;
   font-size: small;
   margin: 0;
   overflow-x: hidden;
 }
 
 #ntp-contents {
   text-align: -webkit-center;
 }
 
-#ntp-contents.classical {
-  margin-top: 157px;
-}
-
-#ntp-contents.md {
-  margin-top: 157px;
-}
-
 .non-google-page #ntp-contents {
-  margin-top: 0;
   position: absolute;
   top: calc(50% - 155px);
   width: 100%;
 }
 
 body.hide-fakebox-logo #logo,
 body.hide-fakebox-logo #fakebox {
   visibility: hidden;
 }
 
 body.fakebox-disable #fakebox {
   border-color: rgb(238, 238, 238);
   cursor: default;
 }
 
 body.fakebox-disable #fakebox > input {
   cursor: default;
 }
 
 #logo {
   background-image: url('images/google_logo.png@2x');
   background-repeat: no-repeat;
   background-size: 269px 95px;
   height: 95px;
   margin-bottom: 24px;
+  margin-top: 157px;
   width: 269px;
 }
 
 body.alternate-logo #logo {
   -webkit-mask-image: url('images/google_logo.png@2x');
   -webkit-mask-repeat: no-repeat;
   -webkit-mask-size: 100%;
   background: #eee;
 }
 
@@ skipping 49 matching lines @@
 
 #fakebox-text {
   color: #bbb;
   font-family: arial, sans-serif;
   font-size: 16px;
   height: 100%;
   left: 9px;
   margin-top: 1px;
   overflow: hidden;
   position: absolute;
-  text-align: left;
+  text-align: initial;
   text-overflow: ellipsis;
   vertical-align: middle;
   visibility: inherit;
   white-space: nowrap;
   width: calc(100% - 2 * 9px);
 }
 
 body[dir=rtl] #fakebox-text {
   left: auto;
   right: 9px;
@@ skipping 556 matching lines @@
   opacity: 0.9;
   padding: 3px;
   position: fixed;
   right: 8px;
 }
 
 body[dir=rtl] #attribution,body[dir=rtl] #recent-tabs {
   left: 8px;
   right: auto;
 }