[DirectWrite] Limit noSubpixelForSmallSizeFont to low-DPI

Source/platform/fonts/FontCache.h

 /*
  * Copyright (C) 2006, 2008 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2007-2008 Torch Mobile, Inc.
  *
  * 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 86 matching lines @@
     void invalidate();
 
 #if OS(WIN)
     PassRefPtr<SimpleFontData> fontDataFromDescriptionAndLogFont(const FontDescription&, ShouldRetain, const LOGFONT&, wchar_t* outFontFamilyName);
 #endif
 
 #if OS(WIN)
     bool useSubpixelPositioning() const { return s_useSubpixelPositioning; }
     SkFontMgr* fontManager() { return m_fontManager.get(); }
     static bool useDirectWrite() { return s_useDirectWrite; }
+    static float deviceScaleFactor() { return s_deviceScaleFactor; }
     static void setUseDirectWrite(bool useDirectWrite) { s_useDirectWrite = useDirectWrite; }
     static void setDirectWriteFactory(IDWriteFactory* factory) { s_directWriteFactory = factory; }
+    static void setDeviceScaleFactor(float deviceScaleFactor) { s_deviceScaleFactor = deviceScaleFactor; }
     static void setUseSubpixelPositioning(bool useSubpixelPositioning) { s_useSubpixelPositioning = useSubpixelPositioning; }
     static void addSideloadedFontForTesting(SkTypeface*);
 #endif
 
 #if ENABLE(OPENTYPE_VERTICAL)
     typedef uint32_t FontFileKey;
     PassRefPtr<OpenTypeVerticalData> getVerticalData(const FontFileKey&, const FontPlatformData&);
 #endif
 
 #if OS(ANDROID)
@@ skipping 36 matching lines @@
     PassRefPtr<SimpleFontData> fontDataFromFontPlatformData(const FontPlatformData*, ShouldRetain = Retain);
     PassRefPtr<SimpleFontData> fallbackOnStandardFontStyle(const FontDescription&, UChar32);
 
     // Don't purge if this count is > 0;
     int m_purgePreventCount;
 
 #if OS(WIN)
     OwnPtr<SkFontMgr> m_fontManager;
     static bool s_useDirectWrite;
     static IDWriteFactory* s_directWriteFactory;
+    static float s_deviceScaleFactor;
     static bool s_useSubpixelPositioning;
     static HashMap<String, RefPtr<SkTypeface> >* s_sideloadedFonts;
 #endif
 
 #if OS(MACOSX) || OS(ANDROID)
     friend class ComplexTextController;
 #endif
     friend class SimpleFontData; // For fontDataFromFontPlatformData
     friend class FontFallbackList;
 };
 
 class PLATFORM_EXPORT FontCachePurgePreventer {
 public:
     FontCachePurgePreventer() { FontCache::fontCache()->disablePurging(); }
     ~FontCachePurgePreventer() { FontCache::fontCache()->enablePurging(); }
 };
 
 } // namespace blink
 
 #endif