Since the constructor is also the class object itself, allowing it to
retroactively become a strong object would have unintuitive consequences
wrt the strength of the other functions of the class, and whether instances
would be considered instances of a strong class.

BUG=v8:3956
LOG=N

Review URL: https://codereview.chromium.org/1314203002

Cr-Commit-Position: refs/heads/master@{#30519}