enforce 16byte alignment in shader contexts

src/effects/gradients/SkRadialGradient.h

Index: src/effects/gradients/SkRadialGradient.h
diff --git a/src/effects/gradients/SkRadialGradient.h b/src/effects/gradients/SkRadialGradient.h
index 9d98f183040eac35ba6d73e2426a35908c9697ea..428d7fae79e1e8d88247ba53e04a28f12c7f3607 100644
--- a/src/effects/gradients/SkRadialGradient.h
+++ b/src/effects/gradients/SkRadialGradient.h
@@ -15,8 +15,6 @@ class SkRadialGradient : public SkGradientShaderBase {
 public:
     SkRadialGradient(const SkPoint& center, SkScalar radius, const Descriptor&);
 
-    size_t contextSize(const ContextRec&) const override;
-
     class RadialGradientContext : public SkGradientShaderBase::GradientShaderBaseContext {
     public:
         RadialGradientContext(const SkRadialGradient&, const ContextRec&);
@@ -41,6 +39,7 @@ public:
 protected:
     SkRadialGradient(SkReadBuffer& buffer);
     void flatten(SkWriteBuffer& buffer) const override;
+    size_t onContextSize(const ContextRec&) const override;
     Context* onCreateContext(const ContextRec&, void* storage) const override;
 
 private: