Metadata not stored correctly using Safari + Webpack

[kdubb]

Environment

Any Safari browser with client code that is webpacked.

Description

Expected behavior:

JsonProperty and its siblings annotations are stored correctly against constructor parameters.

Current behavior:

Annotations used against constructor parameters are stored against the wrong object and then are "missing" when the code attempts to read them back.

Steps to reproduce

1. Build package that serializes/deserializes by using JsonProperty annotations on typescript constructor property definitions.
2. Use package in app that is webpack'd (e.g. using Angular in production mode)
3. Attempt to use code that serializes/deserializes; which fails due to missing JsonProperty metadata.