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

BUG=skia:
R=scroggo@google.com, dominikg@chromium.org

Author: reed@google.com

Review URL: https://codereview.chromium.org/264843006

git-svn-id: http://skia.googlecode.com/svn/trunk@14514 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index 6d753a9..d376b22 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -253,9 +253,8 @@
 }
 
 SkGradientShaderBase::GradientShaderBaseContext::GradientShaderBaseContext(
-        const SkGradientShaderBase& shader, const SkBitmap& device,
-        const SkPaint& paint, const SkMatrix& matrix)
-    : INHERITED(shader, device, paint, matrix)
+        const SkGradientShaderBase& shader, const ContextRec& rec)
+    : INHERITED(shader, rec)
     , fCache(shader.refCache(getPaintAlpha()))
 {
     const SkMatrix& inverse = this->getTotalInverse();