Change GrTextContext fallbacks to be a linked list chain.

src/gpu/GrTextContext.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrTextContext_DEFINED
 #define GrTextContext_DEFINED
 
 #include "GrGlyph.h"
 #include "GrPaint.h"
 #include "SkDeviceProperties.h"
 
 #include "SkPostConfig.h"
 
 class GrContext;
 class GrDrawTarget;
 class GrFontScaler;
 
 /*
  * This class wraps the state for a single text render
  */
 class GrTextContext {
 public:
-    virtual ~GrTextContext() {}
+    virtual ~GrTextContext();
 
-    virtual bool canDraw(const SkPaint& paint) = 0;
-
-    virtual void drawText(const GrPaint&, const SkPaint&, const char text[], size_t byteLength,
-                          SkScalar x, SkScalar y) = 0;
-    virtual void drawPosText(const GrPaint&, const SkPaint&,
-                             const char text[], size_t byteLength,
-                             const SkScalar pos[], int scalarsPerPosition,
-                             const SkPoint& offset) = 0;
+    bool drawText(const GrPaint&, const SkPaint&, const char text[], size_t byteLength,
+                  SkScalar x, SkScalar y);
+    bool drawPosText(const GrPaint&, const SkPaint&,
+                     const char text[], size_t byteLength,
+                     const SkScalar pos[], int scalarsPerPosition,
+                     const SkPoint& offset);
 
 protected:
+    GrTextContext*     fFallbackTextContext;
     GrContext*         fContext;
     SkDeviceProperties fDeviceProperties;
 
     GrDrawTarget*      fDrawTarget;
     SkIRect            fClipRect;
     GrPaint            fPaint;
     SkPaint            fSkPaint;
 
     GrTextContext(GrContext*, const SkDeviceProperties&);
 
+    virtual bool canDraw(const SkPaint& paint) = 0;
+
+    virtual void onDrawText(const GrPaint&, const SkPaint&, const char text[], size_t byteLength,
+                            SkScalar x, SkScalar y) = 0;
+    virtual void onDrawPosText(const GrPaint&, const SkPaint&,
+                               const char text[], size_t byteLength,
+                               const SkScalar pos[], int scalarsPerPosition,
+                               const SkPoint& offset) = 0;
+
     void init(const GrPaint&, const SkPaint&);
     void finish() { fDrawTarget = NULL; }
 
     static GrFontScaler* GetGrFontScaler(SkGlyphCache* cache);
     static void MeasureText(SkGlyphCache* cache, SkDrawCacheProc glyphCacheProc,
                             const char text[], size_t byteLength, SkVector* stopVector);
 };
 
 #endif