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

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

Index: third_party/WebKit/Source/core/css/CSSValuePool.cpp
diff --git a/third_party/WebKit/Source/core/css/CSSValuePool.cpp b/third_party/WebKit/Source/core/css/CSSValuePool.cpp
index 12c18bcac68ca040c43b877657f1014237f302e8..73f4b77a9a40e1e4ba7f2f52f94a7fff65101136 100644
--- a/third_party/WebKit/Source/core/css/CSSValuePool.cpp
+++ b/third_party/WebKit/Source/core/css/CSSValuePool.cpp
@@ -34,6 +34,7 @@ namespace blink {
 
 CSSValuePool& cssValuePool()
 {
+    DCHECK(isMainThread());
     DEFINE_STATIC_LOCAL(CSSValuePool, pool, (new CSSValuePool));
     return pool;
 }
@@ -79,14 +80,6 @@ RawPtr<CSSColorValue> CSSValuePool::createColorValue(RGBA32 rgbValue)
     if (rgbValue == Color::black)
         return m_colorBlack;
 
-    if (!isMainThread()) {
-        // TODO (crbug.com/599659): Make CSS color parsing work properly in a
-        // worker thread.
-        // Currently, ColorValueCache is not thread-safe; so we avoid interacting
-        // with it on a non-main thread.
-        return CSSColorValue::create(rgbValue);
-    }
-
     // Just wipe out the cache and start rebuilding if it gets too big.
     const unsigned maximumColorCacheSize = 512;
     if (m_colorValueCache.size() > maximumColorCacheSize)