[DevTools] Fix search results hover and click area.

third_party/WebKit/Source/devtools/front_end/sources/fileBasedSearchResultsPane.css

 /*
  * Copyright 2016 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.
  */
 
 :host {
     padding: 0;
     margin: 0;
 }
@@ skipping 73 matching lines @@
     background-color: #F1EA00;
 }
 
 :host-context(.-theme-with-dark-background) li.search-match .highlighted-match {
     background-color: hsl(133, 100%, 30%) !important;
 }
 
 .tree-outline a {
     text-decoration: none;
     display: block;
+    flex: auto;
 }
 
 li.search-match .search-match-content {
     color: #000;
 }