For font weights >= 600, create bold system fonts.

Source/platform/fonts/win/FontCacheSkiaWin.cpp

 /*
  * Copyright (C) 2006, 2007 Apple Computer, Inc.
  * Copyright (c) 2006, 2007, 2008, 2009, 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 206 matching lines @@
     // really used.
     // FIXME: Do we need to use predefined fonts "guaranteed" to exist
     // when we're running in layout-test mode?
     if (!typefacesMatchesFamily(tf.get(), creationParams.family())) {
         return 0;
     }
 
     FontPlatformData* result = new FontPlatformData(tf,
         name.data(),
         fontSize,
-        fontDescription.weight() >= FontWeightBold && !tf->isBold() || fontDescription.isSyntheticBold(),
+        fontDescription.weight() >= FontWeight600 && !tf->isBold() || fontDescription.isSyntheticBold(),
         fontDescription.style() == FontStyleItalic && !tf->isItalic() || fontDescription.isSyntheticItalic(),
         fontDescription.orientation(),
         s_useSubpixelPositioning);
 
     struct FamilyMinSize {
         const wchar_t* family;
         unsigned minSize;
     };
     const static FamilyMinSize minAntiAliasSizeForFont[] = {
         { L"simsun", 11 },
         { L"dotum", 12 },
         { L"gulim", 12 },
         { L"pmingliu", 11 }
     };
     size_t numFonts = WTF_ARRAY_LENGTH(minAntiAliasSizeForFont);
     for (size_t i = 0; i < numFonts; i++) {
         FamilyMinSize entry = minAntiAliasSizeForFont[i];
         if (typefacesMatchesFamily(tf.get(), entry.family)) {
             result->setMinSizeForAntiAlias(entry.minSize);
             break;
         }
     }
 
     return result;
 }
 
 }