Gallery: Set the width of name input box exact 100%.

ui/file_manager/gallery/css/gallery.css

 /* Copyright (c) 2014 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 {
   -webkit-user-select: none;
   font-size: 84%;
   margin: 0;
 }
 
@@ skipping 285 matching lines @@
   position: absolute;
   transition: visibility 0ms linear 180ms, all 180ms linear;
   width: 260px;
 }
 
 .gallery .filename-spacer * {
   color: white;
 }
 
 .gallery .filename-spacer .namebox {
-  height: 22px;
-  top: 15px;
-}
-
-.gallery[editing] .filename-spacer .namebox {
-  height: 21px;
-  top: 5px;
-}
-
-.gallery .filename-spacer .namebox {
   background-color: transparent;
   border: none;
   box-sizing: border-box;
   cursor: pointer;
   display: block;
   font-size: 120%;
+  height: 22px;
   outline: none;
   overflow: hidden;
   padding: 0 3px;
   position: absolute;
   text-overflow: ellipsis;
+  top: 15px;
   white-space: nowrap;
+  width: 100%;
+}
+
+.gallery[editing] .filename-spacer .namebox {
+  height: 21px;
+  top: 5px;
 }
 
 .gallery .filename-spacer .namebox[disabled] {
   -webkit-user-select: none;
   cursor: default;
 }
 
 .gallery .filename-spacer .namebox:not([disabled]):not(:focus):hover {
   background-color: rgba(48, 48, 48, 1.0);
 }
@@ skipping 1018 matching lines @@
   background-color: rgba(255, 0, 0, 0.3);
 }
 
 .debug-me .load-target-external-metadata::before {
   background-color: rgba(0, 255, 0, 0.3);
 }
 
 .debug-me .load-target-file-entry::before {
   background-color: rgba(0, 0, 255, 0.3);
 }