Enforce 16byte alignment in shader contexts (patchset #1 id:1 of https://codereview.chromium.org/1759653004/ )"

This reverts commit e38bcaf24b00066e167e03a5ac63cf828914d747.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1763973002

TBR=

Review URL: https://codereview.chromium.org/1763973002
diff --git a/experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.cpp b/experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.cpp
index a5a2a21..a1784a4 100644
--- a/experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.cpp
+++ b/experimental/SkPerlinNoiseShader2/SkPerlinNoiseShader2.cpp
@@ -571,8 +571,8 @@
     return new (storage) PerlinNoiseShaderContext(*this, rec);
 }
 
-size_t SkPerlinNoiseShader2::contextSize(const ContextRec&) const {
-    return sizeof(PerlinNoiseShaderContext);
+size_t SkPerlinNoiseShader2::onContextSize(const ContextRec&) const {
+    return SkAlign16(sizeof(PerlinNoiseShaderContext));
 }
 
 SkPerlinNoiseShader2::PerlinNoiseShaderContext::PerlinNoiseShaderContext(