Issue 6957 - Skip selector lookup for unknown domains

lib/elemHide.js

Index: lib/elemHide.js
===================================================================
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -354,33 +354,39 @@
 
   /**
    * Generates a style sheet for a given domain based on the current set of
    * filters.
    *
    * @param {string} domain The domain.
    * @param {boolean} [specificOnly=false] Whether selectors from generic
    *   filters should be included.
+   * @param {boolean} [includeSelectors=true] Whether the return value should
+   *   include a separate list of selectors.
    *
    * @returns {ElemHideStyleSheet} An object containing the CSS code and the
    *   list of selectors.
    */
-  generateStyleSheetForDomain(domain, specificOnly = false)
+  generateStyleSheetForDomain(domain, specificOnly = false,
+                              includeSelectors = true)
   {
     let knownSuffix = domain ? getKnownSuffix(domain) : "";
 
-    let selectors = getConditionalSelectorsForDomain(knownSuffix, specificOnly);
+    let selectors = [];
+    if (includeSelectors || knownSuffix != "")
+      selectors = getConditionalSelectorsForDomain(knownSuffix, specificOnly);
+
     let code = specificOnly ? createStyleSheet(selectors) :
                  knownSuffix == "" ? getCommonStyleSheet() :
                    (getDefaultStyleSheet() + createStyleSheet(selectors));
 
-    if (!specificOnly)
+    if (includeSelectors && !specificOnly)
       selectors = getUnconditionalSelectors().concat(selectors);
 
-    return {code, selectors};
+    return {code, selectors: includeSelectors ? selectors : null};
   }
 };
 
 /**
  * Splits a list of selectors into groups determined by the value of
  * <code>{@link selectorGroupSize}</code>.
  *
  * @param {Array.<string>} selectors