Make CSSValuePool thread local to ensure correct parsing in colors on workers

third_party/WebKit/Source/core/dom/ExecutionContext.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2012 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 255 matching lines @@
         UseCounter::count(this, UseCounter::ResetReferrerPolicy);
 
     m_referrerPolicy = referrerPolicy;
 }
 
 void ExecutionContext::removeURLFromMemoryCache(const KURL& url)
 {
     memoryCache()->removeURLFromCache(url);
 }
 
+CSSValuePool* ExecutionContext::localCssValuePool()
+{
+    // Local CSS caches are only for worker threads.
+    if (!this->isWorkerGlobalScope())
+        return nullptr;
+
+    // Lazily initialization to avoid unnecessary CSS caches.
+    if (!m_localCssValuePool)
+        m_localCssValuePool = new CSSValuePool();
+    return m_localCssValuePool;
+}
+
 DEFINE_TRACE(ExecutionContext)
 {
     visitor->trace(m_publicURLManager);
+    visitor->trace(m_localCssValuePool);
     ContextLifecycleNotifier::trace(visitor);
     Supplementable<ExecutionContext>::trace(visitor);
 }
 
 } // namespace blink