Add Convert/Make factory functions to FieldAccess.

Change-Id: Ib1f5296c017374b833654f988ff89d11d8f78b4d
Bug: skia:11342
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/380458
Reviewed-by: Brian Osman <brianosman@google.com>
diff --git a/src/sksl/SkSLRehydrator.cpp b/src/sksl/SkSLRehydrator.cpp
index 107fd7c..8007c92 100644
--- a/src/sksl/SkSLRehydrator.cpp
+++ b/src/sksl/SkSLRehydrator.cpp
@@ -469,7 +469,7 @@
             std::unique_ptr<Expression> base = this->expression();
             int index = this->readU8();
             FieldAccess::OwnerKind ownerKind = (FieldAccess::OwnerKind) this->readU8();
-            return std::make_unique<FieldAccess>(std::move(base), index, ownerKind);
+            return FieldAccess::Make(fContext, std::move(base), index, ownerKind);
         }
         case Rehydrator::kFloatLiteral_Command: {
             const Type* type = this->type();