add localMatrix to gradient Descriptor

this consolidation will also help transisition to new flattening pattern, where we want to
have a flatten/unflatten method on all of the common gradient params (i.e. Descriptor).

BUG=skia:
R=egdaniel@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/461643002
diff --git a/src/effects/gradients/SkRadialGradient.cpp b/src/effects/gradients/SkRadialGradient.cpp
index 8a378aa..a6a2e36 100644
--- a/src/effects/gradients/SkRadialGradient.cpp
+++ b/src/effects/gradients/SkRadialGradient.cpp
@@ -145,11 +145,10 @@
 
 /////////////////////////////////////////////////////////////////////
 
-SkRadialGradient::SkRadialGradient(const SkPoint& center, SkScalar radius,
-                                   const Descriptor& desc, const SkMatrix* localMatrix)
-    : SkGradientShaderBase(desc, localMatrix),
-      fCenter(center),
-      fRadius(radius)
+SkRadialGradient::SkRadialGradient(const SkPoint& center, SkScalar radius, const Descriptor& desc)
+    : SkGradientShaderBase(desc)
+    , fCenter(center)
+    , fRadius(radius)
 {
     // make sure our table is insync with our current #define for kSQRT_TABLE_SIZE
     SkASSERT(sizeof(gSqrt8Table) == kSQRT_TABLE_SIZE);