History: Prevent search box from disappearing when search term is deleted.

chrome/browser/resources/history/history_mobile.css

 /* Copyright (c) 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. */
 
 /* This file contains styles specific to Android and iOS. */
 
 html {
   height: 100%;
 }
 
@@ skipping 63 matching lines @@
   display: block;
   line-height: 1.5;
   margin-top: 16px;
   width: 100%;
 }
 
 html[dir='rtl'] #search-field {
   background-position: right 16px center;
 }
 
-/* Hide the search field if it is empty (!valid) and there are no results. */
-body:not(.has-results) #search-field:not(:valid) {
-  display: none;
-}
-
 .no-results-message {
   margin-bottom: 1em;
   padding-left: 16px;
   padding-right: 16px;
 }
 
 .search-results .no-results-message {
   margin-top: 1em;
 }
 
@@ skipping 197 matching lines @@
 
 h1,
 #notification-bar,
 #loading-spinner,
 .no-results-message {
   padding-left: 0;
   padding-right: 0;
 }
 
 } /* @media only screen and (max-width:720px) */