Add "Keep chrome running in background" preference.

chrome/app/chromium_strings.grd

 <?xml version="1.0" encoding="UTF-8"?>
 <!-- This file contains definitions of strings that are distribution specific.
 These strings will not be translated and only english versions will
 be available for now. -->
 
 <grit base_dir="." latest_public_release="0" current_release="1"
       source_lang_id="en" enc_check="möl">
   <outputs>
     <output filename="grit/chromium_strings.h" type="rc_header">
       <emit emit_type='prepend'></emit>
@@ skipping 318 matching lines @@
       <if expr="not pp_ifdef('chromeos')">
         <message name="IDS_OPTIONS_RELAUNCH_REQUIRED" desc="The message displayed for an option that requires a relaunch to take effect. This appears in a message box if an option is changed that requires a relaunch.">
           Please close all Chromium windows and relaunch Chromium for this change to take effect.
         </message>
       </if>
       <if expr="pp_ifdef('chromeos')">
         <message name="IDS_OPTIONS_RELAUNCH_REQUIRED" desc="The message displayed for an option that requires a relaunch to take effect. This appears in a message box if an option is changed that requires a relaunch.">
           Please sign out of Chromium OS and sign in again for this change to take effect.
         </message>
       </if>
+      <message name="IDS_STATUS_TRAY_KEEP_CHROME_RUNNING_IN_BACKGROUND" desc="The checkbox in the status tray context menu that controls whether chrome keeps running in the background after the last window is closed">
+        Let Chromium Run In The Background
+      </message>
+      <message name="IDS_OPTIONS_BACKGROUND_ENABLE_BACKGROUND_MODE" desc="The label of the check-box that enables background mode">
+        Continue running background apps when Chromium is closed
+      </message>
+      <message name="IDS_CONFIRM_EXIT_BACKGROUND_MODE_BODY" desc="Confirmation displayed when disabling background mode via the status tray context menu when there are no windows open">
+        Are you sure you want to quit Chromium? (This setting can be toggled in <ph name="OPTIONS_MENU_LABEL">$1<ex>Options</ex></ph> - Under the Hood)
+      </message>
       <message name="IDS_CANT_WRITE_USER_DIRECTORY_SUMMARY" desc="Summary of problem displayed in dialog when we can't create a directory for this user.">
         Chromium cannot read and write to its data directory:\n\n<ph name="USER_DATA_DIRECTORY">$1<ex>C:\Documents and Settings\devint\Local Settings\Application Data\Google\Chrome</ex></ph>
       </message>
       <message name="IDS_EULA_CHECKBOX_ENABLE_LOGGING" desc="The label of the checkbox to enable/disable crash and user metrics logging">
         Optional: Help make Chromium better by automatically sending usage statistics and crash reports to Google.
       </message>
       <message name="IDS_PROFILE_TOO_NEW_ERROR" desc="Error displayed on startup when the profile is from a newer version of the product and can not be read">
         Your profile can not be used because it is from a newer version of Chromium.\n\nSome features may be unavailable. Please specify a different profile directory or use a newer version of Chromium.
       </message>
       <message name="IDS_PREFERENCES_UNREADABLE_ERROR" desc="Error displayed on startup when user preferences file can not be read">
@@ skipping 186 matching lines @@
         <message name="IDS_UTILITY_APP_NAME" desc="The utility application's name.  Should contain the Chrome application name (IDS_PRODUCT_NAME). Example: Google Chrome Utility.">
           Chromium Utility
         </message>
         <message name="IDS_SHORT_UTILITY_APP_NAME" desc="The utility application's short name, used for the Mac's application menu, activity monitor, etc. Example: Chrome Utility, not Google Chrome Utility.">
           Chromium Utility
         </message>
       </if>
     </messages>
   </release>
 </grit>