Adding a new SkSurface factory for generating surfaces from the scratch texture pool.

include/core/SkSurface.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 SkSurface_DEFINED
 #define SkSurface_DEFINED
 
@@ skipping 55 matching lines @@
      *  Return a new surface using the specified render target.
      */
     static SkSurface* NewRenderTargetDirect(GrRenderTarget*);
 
     /**
      *  Return a new surface whose contents will be drawn to an offscreen
      *  render target, allocated by the surface.
      */
     static SkSurface* NewRenderTarget(GrContext*, const SkImageInfo&, int sampleCount = 0);
 
+    /**
+     *  Return a new surface whose contents will be drawn to an offscreen
+     *  render target, allocated by the surface from the scratch texture pool
+     *  managed by the GrContext. The scratch texture pool serves the purpose
+     *  of retaining textures after they are no longer in use in order to
+     *  re-use them later without having to re-allocate.  Scratch textures
+     *  should be used in cases where high turnover is expected. This allows,
+     *  for example, the copy on write to recycle a texture from a recently
+     *  released SkImage snapshot of the surface.
+     *  Note: Scratch textures count against the GrContext's cached resource
+     *  budget.
+     */
+    static SkSurface* NewScratchRenderTarget(GrContext*, const SkImageInfo&, int sampleCount = 0);
+
     int width() const { return fWidth; }
     int height() const { return fHeight; }
 
     /**
      *  Returns a unique non-zero, unique value identifying the content of this
      *  surface. Each time the content is changed changed, either by drawing
      *  into this surface, or explicitly calling notifyContentChanged()) this
      *  method will return a new value.
      *
      *  If this surface is empty (i.e. has a zero-dimention), this will return
@@ skipping 85 matching lines @@
 
 private:
     const int   fWidth;
     const int   fHeight;
     uint32_t    fGenerationID;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif