Add installer::SetupSingleton.

chrome/app/google_chrome_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <!-- This file contains definitions of strings that are specific to
 Google Chrome. These strings will be translated for each locale that Google
 Chrome supports. If you update this file, be sure also to update
 chromium_strings.grd. -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       output_all_resource_defines="false" source_lang_id="en" enc_check="möl">
   <outputs>
     <output filename="grit/google_chrome_strings.h" type="rc_header">
@@ skipping 421 matching lines @@
         </message>
         <message name="IDS_SETUP_PATCH_FAILED" desc="Error message when setup.exe fails to patch itself.">
           Installation failed due to unspecified error. Please download Google Chrome again.
         </message>
         <message name="IDS_INSTALL_OS_NOT_SUPPORTED" desc="Error displayed if OS is not supported">
           Google Chrome requires Windows 7 or higher.
         </message>
         <message name="IDS_INSTALL_OS_ERROR" desc="Error displayed when any Windows API call fails and we do not have more specific information.">
           An operating system error occurred during installation. Please download Google Chrome again.
         </message>
+        <message name="IDS_INSTALL_SINGLETON_ACQUISITION_FAILED" desc="Error displayed when the installer cannot run because another installer is already running.">
+          Another operation on Google Chrome is in progress. Please try again later.
+        </message>
         <message name="IDS_INSTALL_TEMP_DIR_FAILED" desc="Error displayed when we fail to create temporary directory during installation.">
           The installer couldn't create a temporary directory. Please check for free disk space and permission to install software.
         </message>
         <message name="IDS_INSTALL_UNCOMPRESSION_FAILED" desc="Error when when we can not uncompress installation archive.">
           The installer failed to uncompress archive. Please download Google Chrome again.
         </message>
         <message name="IDS_INSTALL_INVALID_ARCHIVE" desc="Error displayed when we can not open the installation archive.">
           The installer archive is corrupted or invalid. Please download Google Chrome again.
         </message>
         <message name="IDS_INSTALL_INSUFFICIENT_RIGHTS" desc="Error displayed when a non admin user tries to attempt system level install/uninstall.">
@@ skipping 806 matching lines @@
         </message>
         <message name="IDS_METRO_FLOW_LOGO_STRING_ALT"
                  desc="Alt text for the faded Chrome logo image.">
           Chrome logo
         </message>
       </if>
 
     </messages>
   </release>
 </grit>