enforce 16byte alignment in shader contexts

src/effects/gradients/SkRadialGradient.cpp

Index: src/effects/gradients/SkRadialGradient.cpp
diff --git a/src/effects/gradients/SkRadialGradient.cpp b/src/effects/gradients/SkRadialGradient.cpp
index 466ae045a5bbb9c896dead805727ca646f8c6719..da4c6f241284bb995f03ba9daefd973a667cf459 100644
--- a/src/effects/gradients/SkRadialGradient.cpp
+++ b/src/effects/gradients/SkRadialGradient.cpp
@@ -40,8 +40,8 @@ SkRadialGradient::SkRadialGradient(const SkPoint& center, SkScalar radius, const
     , fRadius(radius) {
 }
 
-size_t SkRadialGradient::contextSize(const ContextRec&) const {
-    return sizeof(RadialGradientContext);
+size_t SkRadialGradient::onContextSize(const ContextRec&) const {
+    return SkAlign16(sizeof(RadialGradientContext));
 }
 
 SkShader::Context* SkRadialGradient::onCreateContext(const ContextRec& rec, void* storage) const {