Adjust style of the popup dialogs's title in Files.app.

chrome/browser/resources/file_manager/css/common.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. */
 
 /* This file contains "borrowed" copy of standard styles. To simplify merging,
  * when altering, please preserve original property value by adding comments. */
 input.common[type='checkbox'],
 input.common[type='radio'] {
   -webkit-appearance: none;
   border: 1px solid #555;
@@ skipping 640 matching lines @@
 }
 
 body[new-ui] [hidden] {
   display: none;
 }
 
 body[new-ui] .cr-dialog-title {
   -webkit-margin-after: 10px;
   -webkit-margin-end: 20px;
   display: block;
-  font-size: 120%;
-  font-weight: bold;
+  font-size: 125%;

[hirono, 2013/05/29 04:03:02]

Cannot we specify the direct value '15px'?

   white-space: nowrap;
   word-wrap: normal;
 }
 
 body[new-ui] .cr-dialog-text {
   margin: 13px 0;
 }
 
 body[new-ui] .cr-dialog-text,
 body[new-ui] .cr-dialog-title {
@@ skipping 29 matching lines @@
   width: 44px;
 }
 
 body[new-ui] .cr-dialog-close:hover {
   background-image: url('chrome://theme/IDR_CLOSE_DIALOG_H');
 }
 
 body[new-ui] .cr-dialog-close:active {
   background-image: url('chrome://theme/IDR_CLOSE_DIALOG_P');
 }