Add ability to pass through IDWriteFactory so sandbox can control how it's constructed

Source/platform/fonts/FontCache.cpp

 /*
  * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  *
  * 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.
@@ skipping 48 matching lines @@
 {
 }
 #endif // !OS(WIN)
 
 typedef HashMap<FontCacheKey, OwnPtr<FontPlatformData>, FontCacheKeyHash, FontCacheKeyTraits> FontPlatformDataCache;
 
 static FontPlatformDataCache* gFontPlatformDataCache = 0;
 
 #if OS(WIN)
 bool FontCache::s_useDirectWrite = false;
+IDWriteFactory* FontCache::s_directWriteFactory = 0;
 bool FontCache::s_useSubpixelPositioning = false;
 #endif // OS(WIN)
 
 FontCache* FontCache::fontCache()
 {
     DEFINE_STATIC_LOCAL(FontCache, globalFontCache, ());
     return &globalFontCache;
 }
 
 FontPlatformData* FontCache::getFontPlatformData(const FontDescription& fontDescription,
@@ skipping 211 matching lines @@
         clients.append(*it);
 
     ASSERT(numClients == clients.size());
     for (size_t i = 0; i < numClients; ++i)
         clients[i]->fontCacheInvalidated();
 
     purge(ForcePurge);
 }
 
 } // namespace WebCore