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

include/core/SkColorShader.h

Index: include/core/SkColorShader.h
diff --git a/include/core/SkColorShader.h b/include/core/SkColorShader.h
index 9e19a71edaf26a611cc12404bf37e948e4026a2d..f993959715efa581e0b6b9e92e67679ea752aff6 100644
--- a/include/core/SkColorShader.h
+++ b/include/core/SkColorShader.h
@@ -27,10 +27,7 @@ public:
 
     virtual bool isOpaque() const SK_OVERRIDE;
 
-    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 {
         return sizeof(ColorShaderContext);
@@ -38,8 +35,7 @@ public:
 
     class ColorShaderContext : public SkShader::Context {
     public:
-        ColorShaderContext(const SkColorShader& shader, const SkBitmap& device,
-                           const SkPaint& paint, const SkMatrix& matrix);
+        ColorShaderContext(const SkColorShader& shader, const ContextRec&);
 
         virtual uint32_t getFlags() const SK_OVERRIDE;
         virtual uint8_t getSpan16Alpha() const SK_OVERRIDE;