Issue 6957 - Add rulesFromStyleSheet function to ElemHide module

lib/elemHide.js

Index: lib/elemHide.js
===================================================================
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -401,16 +401,39 @@
       }
     }
 
     return {code, selectors: includeSelectors ? selectors : null};
   }
 };
 
 /**
+ * Yields rules from a style sheet returned by
+ * <code>{@link createStyleSheet}</code>.
+ *
+ * @param {string} styleSheet A style sheet returned by
+ *   <code>{@link createStyleSheet}</code>. If the given style sheet is
+ *   <em>not</em> a value previously returned by a call to
+ *   <code>{@link createStyleSheet}</code>, the behavior is undefined.
+ * @yields {string} A rule from the given style sheet.
+ */
+function* rulesFromStyleSheet(styleSheet)
+{
+  let startIndex = 0;
+  while (startIndex < styleSheet.length)
+  {
+    let ruleTerminatorIndex = styleSheet.indexOf("\n", startIndex);
+    yield styleSheet.substring(startIndex, ruleTerminatorIndex);
+    startIndex = ruleTerminatorIndex + 1;
+  }
+}
+
+exports.rulesFromStyleSheet = rulesFromStyleSheet;
+
+/**
  * Splits a list of selectors into groups determined by the value of
  * <code>{@link selectorGroupSize}</code>.
  *
  * @param {Array.<string>} selectors
  * @yields {Array.<string>}
  */
 function* splitSelectors(selectors)
 {