enforce 16byte alignment in shader contexts

src/effects/gradients/SkLinearGradient.h

Index: src/effects/gradients/SkLinearGradient.h
diff --git a/src/effects/gradients/SkLinearGradient.h b/src/effects/gradients/SkLinearGradient.h
index 33ddfc2f9efecc2ea9283bed73229e6b921e1224..f0ce49b8b39571f90ae6ce89bb9ec34d353753d0 100644
--- a/src/effects/gradients/SkLinearGradient.h
+++ b/src/effects/gradients/SkLinearGradient.h
@@ -33,8 +33,6 @@ public:
 
     SkLinearGradient(const SkPoint pts[2], const Descriptor&);
 
-    size_t contextSize(const ContextRec&) const override;
-
     class LinearGradientContext : public SkGradientShaderBase::GradientShaderBaseContext {
     public:
         LinearGradientContext(const SkLinearGradient&, const ContextRec&);
@@ -71,6 +69,7 @@ public:
 protected:
     SkLinearGradient(SkReadBuffer& buffer);
     void flatten(SkWriteBuffer& buffer) const override;
+    size_t onContextSize(const ContextRec&) const override;
     Context* onCreateContext(const ContextRec&, void* storage) const override;
 
 private: