enforce 16byte alignment in shader contexts

src/image/SkImageShader.h

Index: src/image/SkImageShader.h
diff --git a/src/image/SkImageShader.h b/src/image/SkImageShader.h
index d51dc5d4e48ba866531a121442d5d816d1547bd6..07b938d202bdc048fed070b49aad31c5366e862f 100644
--- a/src/image/SkImageShader.h
+++ b/src/image/SkImageShader.h
@@ -16,7 +16,6 @@ public:
     static SkShader* Create(const SkImage*, TileMode tx, TileMode ty, const SkMatrix* localMatrix);
 
     bool isOpaque() const override;
-    size_t contextSize(const ContextRec&) const override;
 
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkImageShader)
@@ -28,6 +27,7 @@ public:
 
 protected:
     void flatten(SkWriteBuffer&) const override;
+    size_t onContextSize(const ContextRec&) const override;
     Context* onCreateContext(const ContextRec&, void* storage) const override;
 
     SkAutoTUnref<const SkImage> fImage;