-5**2 now produces
SyntaxError: Unary operator used immediately before exponentiation expression.
Parenthesis must be used to disambiguate operator precedence.

Bug: v8:6894
Change-Id: I89dd034ff90ee1a49ba61e0c613da534fbf8b41b
Reviewed-on: https://chromium-review.googlesource.com/c/1418592Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Suraj Sharma <surshar@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#59011}