Change GrTextContext fallbacks to be a linked list chain.

src/gpu/GrTextContext.h

Index: src/gpu/GrTextContext.h
diff --git a/src/gpu/GrTextContext.h b/src/gpu/GrTextContext.h
index b82a64840b1f95d28a96bd20bfc0b0f4fbf6139a..8c7e6f394ef3d87e7ce2d195fdd0360316594ab3 100644
--- a/src/gpu/GrTextContext.h
+++ b/src/gpu/GrTextContext.h
@@ -23,7 +23,7 @@ class GrFontScaler;
  */
 class GrTextContext {
 public:
-    virtual ~GrTextContext() {}
+    virtual ~GrTextContext();
 
     virtual bool canDraw(const SkPaint& paint) = 0;
 
@@ -34,7 +34,11 @@ public:
                              const SkScalar pos[], int scalarsPerPosition,
                              const SkPoint& offset) = 0;
 
+    void setFallbackTextContext(GrTextContext* textContext) { fFallbackTextContext = textContext; }
+    GrTextContext* getFallbackTextContext()                 { return fFallbackTextContext; }
+
 protected:
+    GrTextContext*     fFallbackTextContext;
     GrContext*         fContext;
     SkDeviceProperties fDeviceProperties;