Experiment: check if cssTextCache() needs ThreadSpecific<>.

third_party/WebKit/Source/core/css/CSSPrimitiveValue.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 142 matching lines @@
     case CSSValueCurrentcolor:
         return true;
     default:
         return false;
     }
 }
 
 using CSSTextCache = WillBePersistentHeapHashMap<RawPtrWillBeWeakMember<const CSSPrimitiveValue>, String>;
 static CSSTextCache& cssTextCache()
 {
+    // Experiment: verify that this cache is used from non-main threads.
+    RELEASE_ASSERT(isMainThread());
     AtomicallyInitializedStaticReference(ThreadSpecific<CSSTextCache>, cache, new ThreadSpecific<CSSTextCache>());
     return *cache;
 }
 
 CSSPrimitiveValue::UnitType CSSPrimitiveValue::typeWithCalcResolved() const
 {
     if (type() != UnitType::Calc)
         return type();
 
     switch (m_value.calc->category()) {
@@ skipping 670 matching lines @@
         visitor->trace(m_value.calc);
         break;
     default:
         break;
     }
 #endif
     CSSValue::traceAfterDispatch(visitor);
 }
 
 } // namespace blink