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

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

Index: third_party/WebKit/Source/core/dom/ExecutionContext.h
diff --git a/third_party/WebKit/Source/core/dom/ExecutionContext.h b/third_party/WebKit/Source/core/dom/ExecutionContext.h
index c767839a09e476ff16d78d90e516bf222cc05fee..3edb9258f24acb0034336926ee2ddee713551d58 100644
--- a/third_party/WebKit/Source/core/dom/ExecutionContext.h
+++ b/third_party/WebKit/Source/core/dom/ExecutionContext.h
@@ -29,6 +29,7 @@
 #define ExecutionContext_h
 
 #include "core/CoreExport.h"
+#include "core/css/CSSValuePool.h"
 #include "core/dom/ContextLifecycleNotifier.h"
 #include "core/dom/ContextLifecycleObserver.h"
 #include "core/dom/SecurityContext.h"
@@ -156,6 +157,9 @@ public:
     void setReferrerPolicy(ReferrerPolicy);
     ReferrerPolicy getReferrerPolicy() const { return m_referrerPolicy; }
 
+    // Each worker thread has its own CSS values caches.
+    CSSValuePool* localCssValuePool();
+
 protected:
     ExecutionContext();
     virtual ~ExecutionContext();
@@ -194,6 +198,8 @@ private:
     bool m_isRunSuspendableTasksScheduled;
 
     ReferrerPolicy m_referrerPolicy;
+
+    Member<CSSValuePool> m_localCssValuePool;
 };
 
 } // namespace blink