Add restrictions for min and max width of the left nav in Files.app to avoid breaking layout.

chrome/browser/resources/file_manager/css/file_manager.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. */
 
 html {
   height: 100%;
 }
 
 html.col-resize * {
   cursor: col-resize !important;
@@ skipping 147 matching lines @@
   -webkit-box-flex: 1;
   -webkit-box-orient: vertical;
   display: -webkit-box;
 }
 
 /* Roots list at the left. */
 .dialog-sidebar {
   -webkit-box-flex: 0;
   background-color: #e6e6e6;
   display: -webkit-box;
+  max-width: 50%;
+  min-width: 45px;
   overflow: hidden;
   position: relative;
   width: 168px;
 }
 
 /* A vertical splitter between the roots list and the file list. It is actually
   a transparent area centered on the roots list right border.*/
 div.sidebar-splitter {
   -webkit-box-flex: 0;
   cursor: col-resize;
@@ skipping 1442 matching lines @@
 
 #default-action-dialog {
   min-width: 300px;
   width: auto;
 }
 
 .drive-welcome-wrapper {
   /* drive_welcome.css will override it once loaded. */
   display: none;
 }