Abstract away some of the complexity in CSSSelectorWatch by using HashCountedSet

Source/core/dom/CSSSelectorWatch.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 72 matching lines @@
     m_removedSelectors.clear();
     m_timerExpirations = 0;
 }
 
 void CSSSelectorWatch::updateSelectorMatches(const Vector<String>& removedSelectors, const Vector<String>& addedSelectors)
 {
     bool shouldUpdateTimer = false;
 
     for (unsigned i = 0; i < removedSelectors.size(); ++i) {
         const String& selector = removedSelectors[i];
-        HashMap<String, int>::iterator count = m_matchingCallbackSelectors.find(selector);
-        if (count == m_matchingCallbackSelectors.end())
+        if (!m_matchingCallbackSelectors.remove(selector))
             continue;
-        --count->value;
-        if (!count->value) {
-            shouldUpdateTimer = true;
 
-            m_matchingCallbackSelectors.remove(count);
-            if (m_addedSelectors.contains(selector))
-                m_addedSelectors.remove(selector);
-            else
-                m_removedSelectors.add(selector);
-        }
+        // Count reached 0.
+        shouldUpdateTimer = true;
+        if (m_addedSelectors.contains(selector))

[eseidel, 2013/11/11 22:24:31]

Would itr = find(); remove(itr); be "faster"?  Do we care?

+            m_addedSelectors.remove(selector);
+        else
+            m_removedSelectors.add(selector);
     }
 
     for (unsigned i = 0; i < addedSelectors.size(); ++i) {
         const String& selector = addedSelectors[i];
-        HashMap<String, int>::iterator count = m_matchingCallbackSelectors.find(selector);
-        if (count != m_matchingCallbackSelectors.end()) {
-            ++count->value;
+        HashCountedSet<String>::AddResult result = m_matchingCallbackSelectors.add(selector);
+        if (!result.isNewEntry)
             continue;
-        }
+
         shouldUpdateTimer = true;
-
-        m_matchingCallbackSelectors.set(selector, 1);
         if (m_removedSelectors.contains(selector))
             m_removedSelectors.remove(selector);
         else
             m_addedSelectors.add(selector);
     }
 
     if (!shouldUpdateTimer)
         return;
 
     if (m_removedSelectors.isEmpty() && m_addedSelectors.isEmpty()) {
@@ skipping 38 matching lines @@
 
         RefPtr<StyleRule> rule = StyleRule::create();
         rule->wrapperAdoptSelectorList(selectorList);
         rule->setProperties(callbackPropertySet);
         m_watchedCallbackSelectors.append(rule.release());
     }
     m_document.changedSelectorWatch();
 }
 
 } // namespace WebCore