initial preroll api

include/core/SkShader.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkShader_DEFINED
 #define SkShader_DEFINED
@@ skipping 460 matching lines @@
 
     /**
      *  If this shader can be represented by another shader + a localMatrix, return that shader
      *  and, if not NULL, the localMatrix. If not, return NULL and ignore the localMatrix parameter.
      *
      *  Note: the returned shader (if not NULL) will have been ref'd, and it is the responsibility
      *  of the caller to balance that with unref() when they are done.
      */
     virtual SkShader* refAsALocalMatrixShader(SkMatrix* localMatrix) const;
 
+    void preroll() const { this->onPreroll(); }
+
     SK_TO_STRING_VIRT()
     SK_DEFINE_FLATTENABLE_TYPE(SkShader)
 
 protected:
     void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
     bool computeTotalInverse(const ContextRec&, SkMatrix* totalInverse) const;
 
     /**
      *  Your subclass must also override contextSize() if it overrides onCreateContext().
      *  Base class impl returns NULL.
      */
     virtual Context* onCreateContext(const ContextRec&, void* storage) const;
 
+    virtual void onPreroll() const {}
     virtual bool onAsLuminanceColor(SkColor*) const {
         return false;
     }
 private:
     // This is essentially const, but not officially so it can be modified in
     // constructors.
     SkMatrix fLocalMatrix;
 
     // So the SkLocalMatrixShader can whack fLocalMatrix in its SkReadBuffer constructor.
     friend class SkLocalMatrixShader;
 
     typedef SkFlattenable INHERITED;
 };
 
 #endif