Improve CSS Style matching spec compliance

Source/core/css/CSSFontFaceSource.cpp

 /*
  * Copyright (C) 2007, 2008, 2010, 2011 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 37 matching lines @@
     // If the font hasn't loaded or an error occurred, then we've got nothing.
     if (!isValid())
         return nullptr;
 
     if (isLocal()) {
         // We're local. Just return a SimpleFontData from the normal cache.
         return createFontData(fontDescription);
     }
 
     // See if we have a mapping in our FontData cache.
+    // TODO(drott): Check whether losing traits information here is problematic. crbug.com/516677
     FontCacheKey key = fontDescription.cacheKey(FontFaceCreationParams());
 
     RefPtr<SimpleFontData>& fontData = m_fontDataTable.add(key.hash(), nullptr).storedValue->value;
     if (!fontData)
         fontData = createFontData(fontDescription);
     return fontData; // No release, because fontData is a reference to a RefPtr that is held in the m_fontDataTable.
 }
 
 DEFINE_TRACE(CSSFontFaceSource)
 {
     visitor->trace(m_face);
 }
 
 }