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

include/effects/SkPerlinNoiseShader.h

Index: include/effects/SkPerlinNoiseShader.h
diff --git a/include/effects/SkPerlinNoiseShader.h b/include/effects/SkPerlinNoiseShader.h
index 5b270293b16a19b70db7878e67ceb1242772e01e..2766df0a78fc1f25c4ecb7856bbcdfcb5308a8b5 100644
--- a/include/effects/SkPerlinNoiseShader.h
+++ b/include/effects/SkPerlinNoiseShader.h
@@ -72,15 +72,12 @@ public:
     }
 
 
-    virtual SkShader::Context* createContext(
-        const SkBitmap& device, const SkPaint& paint,
-        const SkMatrix& matrix, void* storage) const SK_OVERRIDE;
+    virtual SkShader::Context* createContext(const ContextRec&, void* storage) const SK_OVERRIDE;
     virtual size_t contextSize() const SK_OVERRIDE;
 
     class PerlinNoiseShaderContext : public SkShader::Context {
     public:
-        PerlinNoiseShaderContext(const SkPerlinNoiseShader& shader, const SkBitmap& device,
-                                 const SkPaint& paint, const SkMatrix& matrix);
+        PerlinNoiseShaderContext(const SkPerlinNoiseShader& shader, const ContextRec&);
         virtual ~PerlinNoiseShaderContext() {}
 
         virtual void shadeSpan(int x, int y, SkPMColor[], int count) SK_OVERRIDE;