Issue 2161 - Add an option for disabling element hiding filters

lib/elemHide.js

Index: lib/elemHide.js
===================================================================
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -78,17 +78,17 @@ let ElemHide = exports.ElemHide =
 
   /**
    * Called on module startup.
    */
   init: function()
   {
     Prefs.addListener(function(name)
     {
-      if (name == "enabled")
+      if (name == "enabled" || name == "element_hiding_enabled")
         ElemHide.apply();
     });
     onShutdown.add(function()
     {
       ElemHide.unapply();
     });
 
     let styleFile = IO.resolveFilePath(Prefs.data_directory);
@@ -110,16 +110,19 @@ let ElemHide = exports.ElemHide =
   },
 
   /**
    * Add a new element hiding filter
    * @param {ElemHideFilter} filter
    */
   add: function(filter)
   {
+    if (!Prefs.element_hiding_enabled)
+      return;
+
     if (filter instanceof ElemHideException)
     {
       if (filter.text in knownExceptions)
         return;
 
       let selector = filter.selector;
       if (!(selector in exceptions))
         exceptions[selector] = [];
@@ -207,32 +210,34 @@ let ElemHide = exports.ElemHide =
   apply: function()
   {
     if (this._applying)
     {
       this._needsApply = true;
       return;
     }
 
-    if (!ElemHide.isDirty || !Prefs.enabled)
+    let enabled = Prefs.enabled && Prefs.element_hiding_enabled;
+
+    if (!ElemHide.isDirty || !enabled)
     {
       // Nothing changed, looks like we merely got enabled/disabled
-      if (Prefs.enabled && !ElemHide.applied)
+      if (enabled && !ElemHide.applied)
       {
         try
         {
           Utils.styleService.loadAndRegisterSheet(styleURL, Ci.nsIStyleSheetService.USER_SHEET);
           ElemHide.applied = true;
         }
         catch (e)
         {
           Cu.reportError(e);
         }
       }
-      else if (!Prefs.enabled && ElemHide.applied)
+      else if (!enabled && ElemHide.applied)
       {
         ElemHide.unapply();
       }
 
       return;
     }
 
     IO.writeToFile(styleURL.file, this._generateCSSContent(), function(e)