add SkImage::newSurface

src/image/SkImage_Base.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImage_Base_DEFINED
 #define SkImage_Base_DEFINED
 
 #include "SkImage.h"
 
 class SkImage_Base : public SkImage {
 public:
     SkImage_Base(int width, int height) : INHERITED(width, height) {}
 
     virtual void onDraw(SkCanvas*, SkScalar x, SkScalar y, const SkPaint*) const = 0;
     virtual void onDrawRect(SkCanvas*, const SkRect* src,
                                   const SkRect& dst, const SkPaint*) const = 0;
+    virtual SkSurface* onNewSurface(const SkImageInfo&, const SkSurfaceProps&) const = 0;
 
     // Default impl calls onDraw
     virtual bool onReadPixels(SkBitmap*, const SkIRect& subset) const;
 
     virtual const void* onPeekPixels(SkImageInfo*, size_t* /*rowBytes*/) const {
         return NULL;
     }
 
     virtual GrTexture* onGetTexture() const { return NULL; }
 
     // return a read-only copy of the pixels. We promise to not modify them,
     // but only inspect them (or encode them).
     virtual bool getROPixels(SkBitmap*) const { return false; }
 
     virtual SkShader* onNewShader(SkShader::TileMode,
                                   SkShader::TileMode,
                                   const SkMatrix* localMatrix) const { return NULL; };
+
 private:
     typedef SkImage INHERITED;
 };
 
 #endif