use Descriptor struct to encapsulate all the common paramaeters between our various gradient types. If we like it, might promote it to the public API.

BUG=
R=bsalomon@google.com

Review URL: https://codereview.chromium.org/15733007

git-svn-id: http://skia.googlecode.com/svn/trunk@9260 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/gradients/SkLinearGradient.h b/src/effects/gradients/SkLinearGradient.h
index ff1796b..24c6cab 100644
--- a/src/effects/gradients/SkLinearGradient.h
+++ b/src/effects/gradients/SkLinearGradient.h
@@ -13,9 +13,7 @@
 
 class SkLinearGradient : public SkGradientShaderBase {
 public:
-    SkLinearGradient(const SkPoint pts[2],
-                     const SkColor colors[], const SkScalar pos[], int colorCount,
-                     SkShader::TileMode mode, SkUnitMapper* mapper);
+    SkLinearGradient(const SkPoint pts[2], const Descriptor&);
 
     virtual bool setContext(const SkBitmap&, const SkPaint&, const SkMatrix&) SK_OVERRIDE;
     virtual void shadeSpan(int x, int y, SkPMColor dstC[], int count) SK_OVERRIDE;