Change GrTextContext fallbacks to be a linked list chain.

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
 
 #include "GrTextContext.h"
 
 class GrGeometryProcessor;
 class GrTextStrike;
 
 /*
  * This class implements GrTextContext using distance field fonts
  */
 class GrDistanceFieldTextContext : public GrTextContext {
 public:
-    GrDistanceFieldTextContext(GrContext*, const SkDeviceProperties&, bool enable);
+    static GrDistanceFieldTextContext* Create(GrContext*, const SkDeviceProperties&, bool enable);
+
     virtual ~GrDistanceFieldTextContext();
 
-    virtual bool canDraw(const SkPaint& paint) SK_OVERRIDE;
-
-    virtual void drawText(const GrPaint&, const SkPaint&, const char text[], size_t byteLength,
-                          SkScalar x, SkScalar y) SK_OVERRIDE;
-    virtual void drawPosText(const GrPaint&, const SkPaint&,
-                             const char text[], size_t byteLength,
-                             const SkScalar pos[], int scalarsPerPosition,
-                             const SkPoint& offset) SK_OVERRIDE;
-
 private:
     enum {
         kMinRequestedGlyphs      = 1,
         kDefaultRequestedGlyphs  = 64,
         kMinRequestedVerts       = kMinRequestedGlyphs * 4,
         kDefaultRequestedVerts   = kDefaultRequestedGlyphs * 4,
     };
 
     GrTextStrike*                      fStrike;
     SkScalar                           fTextRatio;
     bool                               fUseLCDText;
     bool                               fEnableDFRendering;
     SkAutoTUnref<GrGeometryProcessor>  fCachedGeometryProcessor;
     // Used to check whether fCachedEffect is still valid.
     uint32_t                           fEffectTextureUniqueID;
     SkColor                            fEffectColor;
     uint32_t                           fEffectFlags;
     GrTexture*                         fGammaTexture;
     void*                              fVertices;
     int32_t                            fMaxVertices;
     GrTexture*                         fCurrTexture;
     int                                fCurrVertex;
     SkRect                             fVertexBounds;
 
+    GrDistanceFieldTextContext(GrContext*, const SkDeviceProperties&, bool enable);
+
+    virtual bool canDraw(const SkPaint& paint) SK_OVERRIDE;
+
+    virtual void onDrawText(const GrPaint&, const SkPaint&, const char text[], size_t byteLength,
+                            SkScalar x, SkScalar y) SK_OVERRIDE;
+    virtual void onDrawPosText(const GrPaint&, const SkPaint&,
+                               const char text[], size_t byteLength,
+                               const SkScalar pos[], int scalarsPerPosition,
+                               const SkPoint& offset) SK_OVERRIDE;
+
     void init(const GrPaint&, const SkPaint&);
     void appendGlyph(GrGlyph::PackedID, SkFixed left, SkFixed top, GrFontScaler*);
     void setupCoverageEffect(const SkColor& filteredColor);
     void flush();                 // automatically called by destructor
     void finish();
 };
 
 #endif