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

src/effects/gradients/SkGradientShaderPriv.h

Index: src/effects/gradients/SkGradientShaderPriv.h
diff --git a/src/effects/gradients/SkGradientShaderPriv.h b/src/effects/gradients/SkGradientShaderPriv.h
index c1e253fd4a3c646d76e3887e9999e9fd6534af14..a699c4ce00b7e4e1672d45517592db1395e8d90f 100644
--- a/src/effects/gradients/SkGradientShaderPriv.h
+++ b/src/effects/gradients/SkGradientShaderPriv.h
@@ -142,9 +142,7 @@ public:
 
     class GradientShaderBaseContext : public SkShader::Context {
     public:
-        GradientShaderBaseContext(const SkGradientShaderBase& shader, const SkBitmap& device,
-                                  const SkPaint& paint, const SkMatrix& matrix);
-        ~GradientShaderBaseContext() {}
+        GradientShaderBaseContext(const SkGradientShaderBase& shader, const ContextRec&);
 
         virtual uint32_t getFlags() const SK_OVERRIDE { return fFlags; }