Add effect caching to distance field text.

src/gpu/GrDistanceFieldTextContext.h

Index: src/gpu/GrDistanceFieldTextContext.h
diff --git a/src/gpu/GrDistanceFieldTextContext.h b/src/gpu/GrDistanceFieldTextContext.h
index 7676fc16482b63e7163e5e661177d15142cd068e..672922d0d64f4dc935ccc248627ee059af332ddf 100644
--- a/src/gpu/GrDistanceFieldTextContext.h
+++ b/src/gpu/GrDistanceFieldTextContext.h
@@ -34,11 +34,17 @@ private:
     SkScalar                fTextRatio;
     bool                    fUseLCDText;
     bool                    fEnableDFRendering;
+    SkAutoTUnref<GrEffect>  fCachedEffect;
+    // Used to check whether fCachedEffect is still valid.
+    uint32_t                fEffectTextureUniqueID;
+    SkColor                 fEffectColor;
+    uint32_t                fEffectFlags;
     GrTexture*              fGammaTexture;
 
     void init(const GrPaint&, const SkPaint&);
     void drawPackedGlyph(GrGlyph::PackedID, SkFixed left, SkFixed top, GrFontScaler*);
     void flushGlyphs();                 // automatically called by destructor
+    void setupCoverageEffect(const SkColor& filteredColor);
     void finish();
 
     enum {