This patch changes the test262 infrastructure to pass individual flags,
specified in the status file, for tests for experimental features, rather
than passing --harmony for all runs. With this change, it should be
easier to run test262 tests in automation when developing new features.
The new workflow would be, when adding a flag, include the flag in the
test expectations file, and when removing the flag, remove the lines from
the test expectations file. This way, the status file does not have to
change when staging or unstaging, and you get the benefit of the automated
tests before staging starts.

R=adamk
CQ_INCLUDE_TRYBOTS=master.tryserver.v8:v8_linux_noi18n_rel_ng

Review-Url: https://codereview.chromium.org/2601393002
Cr-Commit-Position: refs/heads/master@{#42249}