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

src/effects/gradients/SkLinearGradient.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 SkLinearGradient_DEFINED
 #define SkLinearGradient_DEFINED
 
 #include "SkGradientShaderPriv.h"
 
 class SkLinearGradient : public SkGradientShaderBase {
 public:
     SkLinearGradient(const SkPoint pts[2], const Descriptor&, const SkMatrix* localMatrix);
 
-    virtual SkShader::Context* createContext(const SkBitmap&, const SkPaint&, const SkMatrix&,
-                                             void* storage) const SK_OVERRIDE;
+    virtual SkShader::Context* createContext(const ContextRec&, void* storage) const SK_OVERRIDE;
     virtual size_t contextSize() const SK_OVERRIDE;
 
     class LinearGradientContext : public SkGradientShaderBase::GradientShaderBaseContext {
     public:
-        LinearGradientContext(const SkLinearGradient& shader, const SkBitmap& device,
-                              const SkPaint& paint, const SkMatrix& matrix);
+        LinearGradientContext(const SkLinearGradient&, const ContextRec&);
         ~LinearGradientContext() {}
 
         virtual void shadeSpan(int x, int y, SkPMColor dstC[], int count) SK_OVERRIDE;
         virtual void shadeSpan16(int x, int y, uint16_t dstC[], int count) SK_OVERRIDE;
 
     private:
         typedef SkGradientShaderBase::GradientShaderBaseContext INHERITED;
     };
 
     virtual BitmapType asABitmap(SkBitmap*, SkMatrix*, TileMode*) const SK_OVERRIDE;
     virtual GradientType asAGradient(GradientInfo* info) const SK_OVERRIDE;
     virtual GrEffectRef* asNewEffect(GrContext* context, const SkPaint&) const SK_OVERRIDE;
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkLinearGradient)
 
 protected:
     SkLinearGradient(SkReadBuffer& buffer);
     virtual void flatten(SkWriteBuffer& buffer) const SK_OVERRIDE;
 
 private:
     typedef SkGradientShaderBase INHERITED;
     const SkPoint fStart;
     const SkPoint fEnd;
 };
 
 #endif