Remove front-end for nglayout.debug.enable_xpcom_refcnt_log pref, which has no backend. r=ben sr=blake b=156157

suite/common/pref/pref-debug.xul

@@ -33,7 +33,7 @@
     var _elementIDs = ["nglayoutDebugWindow", "nglayoutUseNativePrintDialog", "printUseGlobalPrintSettings",
                        "debugXULBoxes", "browserDOMWindowDumpEnabled", 
                        "javascriptOptionsStrict", "javascriptOptionsShowInConsole", 
-                       "nglayoutDebugUseXBLForms", "nglayoutDebugEnableXPCOMRefcntLog", 
+                       "nglayoutDebugUseXBLForms",
                        "acceleratorKeyValue", "menuAccessKeyValue"];
   ]]>
   </script>
@@ -75,8 +75,6 @@
               prefstring="javascript.options.showInConsole"/>
     <checkbox id="nglayoutDebugUseXBLForms" label="&debugUseXBLForms.label;"
               prefstring="nglayout.debug.enable_xbl_forms"/>
-    <checkbox id="nglayoutDebugEnableXPCOMRefcntLog" label="&debugEnableXPCOMRefcntLog.label;"
-              prefstring="nglayout.debug.enable_xpcom_refcnt_log"/>
   </groupbox>              
 
 

suite/locales/en-US/chrome/common/pref/pref-debug.dtd

@@ -11,7 +11,6 @@
 <!ENTITY debugStrictJavascript.label     "Show strict JavaScript warnings">
 <!ENTITY debugConsoleJavascript.label    "Show Javascript errors and warnings in Mozilla chrome in the js console">
 <!ENTITY debugUseXBLForms.label          "Use XBL-based form controls (takes effect after restart). These are still under construction.">
-<!ENTITY debugEnableXPCOMRefcntLog.label "Enable XPCOM Refcount Log">
 
 <!-- Debug: Turn on gfx-rendered widgets -->
 <!ENTITY widgetRendering.label "Rendering">