Bug 255932: Add 'Warn when closing multiple tabs' pref to Advanced under Browsing. r=blake

browser/components/prefwindow/content/pref-advanced.js

@@ -36,7 +36,7 @@
 #define PROVISIONAL_SECURITY_UI
 
 var _elementIDs = ["moveSystemCaret", "hideTabBar",
-                    "loadInBackground", "useAutoScrolling",
+                    "loadInBackground", "warnOnClose", "useAutoScrolling",
                     "useSmoothScrolling", "enableAutoImageResizing",
                     "useSSL2", "useSSL3", "useTLS1", "useTypeAheadFind",
                     "linksOnlyTypeAheadFind",

browser/components/prefwindow/content/pref-advanced.xul

@@ -33,6 +33,8 @@
                 prefstring="browser.tabs.autoHide"/>
       <checkbox id="loadInBackground" label="&loadInBackground.label;"
                 prefstring="browser.tabs.loadInBackground" reversed="true"/>
+      <checkbox id="warnOnClose" label="&warnOnClose.label;"
+                prefstring="browser.tabs.warnOnClose"/>
       <checkbox id="useAutoScrolling" label="&useAutoScrolling.label;"
                 prefstring="general.autoScroll"/>
       <checkbox id="useSmoothScrolling" label="&useSmoothScrolling.label;"

browser/locales/en-US/chrome/browser/pref/pref-advanced.dtd

@@ -7,6 +7,7 @@
 <!ENTITY browsing.label               "Browsing">
 <!ENTITY hideTabBar.label             "Hide the tab bar when only one website is open">
 <!ENTITY loadInBackground.label       "Select new tabs opened from links">
+<!ENTITY warnOnClose.label            "Warn when closing multiple tabs">
 <!ENTITY useAutoScrolling.label       "Use autoscrolling">
 <!ENTITY useSmoothScrolling.label     "Use smooth scrolling">
 <!ENTITY multimedia.label             "Multimedia">