Small refactoring of layer discovery code

src/gpu/GrPictureUtils.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrPictureUtils_DEFINED
 #define GrPictureUtils_DEFINED
 
@@ skipping 58 matching lines @@
     // We may, in the future, need to pass in the GPUDevice in order to
     // incorporate the clip and matrix state into the key
     static SkPicture::AccelData::Key ComputeAccelDataKey();
 
 private:
     SkTArray<SaveLayerInfo, true> fSaveLayerInfo;
 
     typedef SkPicture::AccelData INHERITED;
 };
 
+void SkRecordComputeLayers(const SkRect& cullRect, const SkRecord& record,
+                           SkBBoxHierarchy* bbh, GrAccelData* data);
+
 const GrAccelData* GPUOptimize(const SkPicture* pict);
 
 #endif // GrPictureUtils_DEFINED