Re-collect rule features for watched selectors.

third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 152 matching lines @@
 {
 }
 
 void StyleResolver::dispose()
 {
     m_matchedPropertiesCache.clear();
 }
 
 void StyleResolver::initWatchedSelectorRules()
 {
+    m_watchedSelectorsRules = nullptr;
     CSSSelectorWatch* watch = CSSSelectorWatch::fromIfExists(*m_document);
     if (!watch)
         return;
     const WillBeHeapVector<RefPtrWillBeMember<StyleRule>>& watchedSelectors = watch->watchedCallbackSelectors();
     if (!watchedSelectors.size())
         return;
     m_watchedSelectorsRules = RuleSet::create();
     for (unsigned i = 0; i < watchedSelectors.size(); ++i)
         m_watchedSelectorsRules->addStyleRule(watchedSelectors[i].get(), RuleHasNoSpecialState);
 }
@@ skipping 1398 matching lines @@
     visitor->trace(m_uncommonAttributeRuleSet);
     visitor->trace(m_watchedSelectorsRules);
     visitor->trace(m_treeBoundaryCrossingScopes);
     visitor->trace(m_styleSharingLists);
     visitor->trace(m_pendingStyleSheets);
     visitor->trace(m_document);
 #endif
 }
 
 } // namespace blink