create struct to hold all the params passed around for shader::context

src/core/SkFilterShader.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 SkFilterShader_DEFINED
 #define SkFilterShader_DEFINED
 
 #include "SkShader.h"
 
 class SkColorFilter;
 
 class SkFilterShader : public SkShader {
 public:
     SkFilterShader(SkShader* shader, SkColorFilter* filter);
     virtual ~SkFilterShader();
 
-    virtual bool validContext(const SkBitmap&, const SkPaint&,
-                              const SkMatrix&, SkMatrix* totalInverse = NULL) const SK_OVERRIDE;
-    virtual SkShader::Context* createContext(const SkBitmap&, const SkPaint&,
-                                             const SkMatrix&, void* storage) const SK_OVERRIDE;
+    virtual bool validContext(const ContextRec&, SkMatrix* totalInverse) const SK_OVERRIDE;
+    virtual SkShader::Context* createContext(const ContextRec&, void* storage) const SK_OVERRIDE;
     virtual size_t contextSize() const SK_OVERRIDE;
 
     class FilterShaderContext : public SkShader::Context {
     public:
         // Takes ownership of shaderContext and calls its destructor.
-        FilterShaderContext(const SkFilterShader& filterShader, SkShader::Context* shaderContext,
-                            const SkBitmap& device, const SkPaint& paint, const SkMatrix& matrix);
+        FilterShaderContext(const SkFilterShader&, SkShader::Context*, const ContextRec&);
         virtual ~FilterShaderContext();
 
         virtual uint32_t getFlags() const SK_OVERRIDE;
 
         virtual void shadeSpan(int x, int y, SkPMColor[], int count) SK_OVERRIDE;
         virtual void shadeSpan16(int x, int y, uint16_t[], int count) SK_OVERRIDE;
 
     private:
         SkShader::Context* fShaderContext;
 
         typedef SkShader::Context INHERITED;
     };
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkFilterShader)
 
 protected:
     SkFilterShader(SkReadBuffer& );
     virtual void flatten(SkWriteBuffer&) const SK_OVERRIDE;
 
 private:
     SkShader*       fShader;
     SkColorFilter*  fFilter;
 
     typedef SkShader INHERITED;
 };
 
 #endif