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

src/effects/gradients/SkRadialGradient.h

Index: src/effects/gradients/SkRadialGradient.h
diff --git a/src/effects/gradients/SkRadialGradient.h b/src/effects/gradients/SkRadialGradient.h
index 7aafe2d1533c954be1637d612cf87f0323d7c547..873024730d4678bb7d3ff1d3894d8f2bb8444a1f 100644
--- a/src/effects/gradients/SkRadialGradient.h
+++ b/src/effects/gradients/SkRadialGradient.h
@@ -16,15 +16,12 @@ public:
     SkRadialGradient(const SkPoint& center, SkScalar radius, 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 RadialGradientContext : public SkGradientShaderBase::GradientShaderBaseContext {
     public:
-        RadialGradientContext(const SkRadialGradient& shader, const SkBitmap& device,
-                              const SkPaint& paint, const SkMatrix& matrix);
-        ~RadialGradientContext() {}
+        RadialGradientContext(const SkRadialGradient&, const ContextRec&);
 
         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;