Add "Keep chrome running in background" preference.

chrome/app/google_chrome_strings.grd

Index: chrome/app/google_chrome_strings.grd
diff --git a/chrome/app/google_chrome_strings.grd b/chrome/app/google_chrome_strings.grd
index 0562ebc31e08e7bf71f5592f85504c6929412ab6..4192c512405e8ff2df9bd703aef264cf80294d83 100644
--- a/chrome/app/google_chrome_strings.grd
+++ b/chrome/app/google_chrome_strings.grd
@@ -342,6 +342,12 @@ Chrome supports. -->
           Please sign out of Chrome OS and sign in again for this change to take effect.
         </message>
       </if>
+      <message name="IDS_OPTIONS_BACKGROUND_ENABLE_BACKGROUND_MODE" desc="The label of the check-box that enables background mode">
+        Continue running background apps when Google Chrome is closed

[Rick Campbell, 2011/05/11 20:33:01]

Perhaps "Continue runnin Chromium in the background after the last window 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 Google Chrome? (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.">
         Google Chrome 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>