CSSSelectorWatch: avoid unnecessary hash table lookups.

third_party/WebKit/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 81 matching lines @@
     const Vector<String>& addedSelectors) {
   bool shouldUpdateTimer = false;
 
   for (unsigned i = 0; i < removedSelectors.size(); ++i) {
     const String& selector = removedSelectors[i];
     if (!m_matchingCallbackSelectors.remove(selector))
       continue;
 
     // Count reached 0.
     shouldUpdateTimer = true;
-    if (m_addedSelectors.contains(selector))
-      m_addedSelectors.remove(selector);
+    auto it = m_addedSelectors.find(selector);
+    if (it != m_addedSelectors.end())
+      m_addedSelectors.remove(it);
     else
       m_removedSelectors.add(selector);
   }
 
   for (unsigned i = 0; i < addedSelectors.size(); ++i) {
     const String& selector = addedSelectors[i];
     HashCountedSet<String>::AddResult result =
         m_matchingCallbackSelectors.add(selector);
     if (!result.isNewEntry)
       continue;
 
     shouldUpdateTimer = true;
-    if (m_removedSelectors.contains(selector))
-      m_removedSelectors.remove(selector);
+    auto it = m_removedSelectors.find(selector);
+    if (it != m_removedSelectors.end())
+      m_removedSelectors.remove(it);
     else
       m_addedSelectors.add(selector);
   }
 
   if (!shouldUpdateTimer)
     return;
 
   if (m_removedSelectors.isEmpty() && m_addedSelectors.isEmpty()) {
     if (m_callbackSelectorChangeTimer.isActive()) {
       m_timerExpirations = 0;
@@ skipping 37 matching lines @@
   document().styleEngine().watchedSelectorsChanged();
 }
 
 DEFINE_TRACE(CSSSelectorWatch) {
   visitor->trace(m_watchedCallbackSelectors);
   visitor->trace(m_document);
   Supplement<Document>::trace(visitor);
 }
 
 }  // namespace blink