These flags have been on by default since version 4.9, which has been
in stable Chrome for over a week now, demonstrating that they're
here to stay.

Also moved the tests out of harmony/ and into es6/.

Review URL: https://codereview.chromium.org/1776683003

Cr-Commit-Position: refs/heads/master@{#34692}

This is in preparation for the addition of --harmony-destructuring-assignment.

BUG=v8:811
LOG=n

Review URL: https://codereview.chromium.org/1450193002

Cr-Commit-Position: refs/heads/master@{#32098}

This allows testing the configuration where --harmony-default-parameters
is passed without --harmony-destructuring.

R=rossberg@chromium.org
BUG=v8:2160
LOG=n

Review URL: https://codereview.chromium.org/1410023015

Cr-Commit-Position: refs/heads/master@{#31863}