Add fallback code for TextContexts that don't support all features

include/gpu/GrTextContext.h

Index: include/gpu/GrTextContext.h
diff --git a/include/gpu/GrTextContext.h b/include/gpu/GrTextContext.h
index 273e0947b11d92b6c4daaf3ba912271b87196c7e..c572d0d016e264e2eeee34b654972ba6addecb77 100644
--- a/include/gpu/GrTextContext.h
+++ b/include/gpu/GrTextContext.h
@@ -29,7 +29,7 @@ public:
     virtual void drawPosText(const char text[], size_t byteLength,
                              const SkScalar pos[], SkScalar constY,
                              int scalarsPerPosition) = 0;
-
+    
 protected:
     GrTextContext(GrContext*, const GrPaint&, const SkPaint&, const SkDeviceProperties&);
 
@@ -55,6 +55,7 @@ public:
     virtual ~GrTextContextManager() {}
     virtual GrTextContext* create(GrContext* grContext, const GrPaint& grPaint,
                                   const SkPaint& skPaint, const SkDeviceProperties& props) = 0;
+    virtual bool canDraw(const SkPaint& paint, const SkMatrix& ctm) = 0;
 };
 
 template <class TextContextClass>
@@ -110,6 +111,10 @@ public:
         return obj;
     }
 
+    virtual bool canDraw(const SkPaint& paint, const SkMatrix& ctm) SK_OVERRIDE {
+        return TextContextClass::CanDraw(paint, ctm);
+    }
+
 private:
     void recycle(GrTextContext* textContext) {
         SkASSERT((void*)textContext == fAllocation);