Emulate gamma fix by making glyphs thicker or thinner

src/gpu/GrDistanceFieldTextContext.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrDistanceFieldTextContext_DEFINED
 #define GrDistanceFieldTextContext_DEFINED
 
@@ skipping 18 matching lines @@
         kDefaultRequestedGlyphs  = 64,
         kMinRequestedVerts       = kMinRequestedGlyphs * 4,
         kDefaultRequestedVerts   = kDefaultRequestedGlyphs * 4,
     };
 
     GrTextStrike*                      fStrike;
     SkScalar                           fTextRatio;
     bool                               fUseLCDText;
     bool                               fEnableDFRendering;
     SkAutoTUnref<GrGeometryProcessor>  fCachedGeometryProcessor;
+    SkScalar*                          fDistanceAdjustTable;
     // Used to check whether fCachedEffect is still valid.
     uint32_t                           fEffectTextureUniqueID;
     SkColor                            fEffectColor;
     uint32_t                           fEffectFlags;
-    GrTexture*                         fGammaTexture;
     void*                              fVertices;
     int                                fCurrVertex;
     int                                fAllocVertexCount;
     int                                fTotalVertexCount;
     GrTexture*                         fCurrTexture;
     SkRect                             fVertexBounds;
     SkMatrix                           fViewMatrix;
 
     GrDistanceFieldTextContext(GrContext*, SkGpuDevice*, const SkDeviceProperties&, bool enable);
+    void buildDistanceAdjustTable();
 
     bool canDraw(const GrRenderTarget*, const GrClip&, const GrPaint&,
                  const SkPaint&, const SkMatrix& viewMatrix) override;
 
     void onDrawText(GrRenderTarget*, const GrClip&, const GrPaint&, const SkPaint&,
                     const SkMatrix& viewMatrix,
                     const char text[], size_t byteLength,
                     SkScalar x, SkScalar y, const SkIRect& regionClipBounds) override;
     void onDrawPosText(GrRenderTarget*, const GrClip&, const GrPaint&, const SkPaint&,
                        const SkMatrix& viewMatrix,
                        const char text[], size_t byteLength,
                        const SkScalar pos[], int scalarsPerPosition,
                        const SkPoint& offset, const SkIRect& regionClipBounds) override;
 
     void init(GrRenderTarget*, const GrClip&, const GrPaint&, const SkPaint&,
               const SkIRect& regionClipBounds);
     bool appendGlyph(GrGlyph::PackedID, SkScalar left, SkScalar top, GrFontScaler*);
     bool uploadGlyph(GrGlyph*, GrFontScaler*);
     void setupCoverageEffect(const SkColor& filteredColor);
     void flush();                 // automatically called by destructor
     void finish();
 };
 
 #endif