refactor(ngScenario/ObjectModel.js): use Date.now() to get current Time

[HAKASHUN]

http://jsperf.com/date-now-vs-new-date-gettime/11

[pkozlowski-opensource]

I think we can merge this now that IE8 is not officially supported. This refactoring won't change much in practice, but it is a bit cleaner - why not.

@HAKASHUN could you please sign the CLA so we can merge this PR?

[lgalfaso]

@pkozlowski-opensource I understand that this can be orthogonal, but would like to see #10525 land first

[pkozlowski-opensource]

@lgalfaso I don't mind either way but yes, it is totally orthogonal and simple refactoring so I wouldn't like to hold this one for too long if we intend to merge this PR. We've got way to many stale ones and I would like to clean up the backlog as much as possible.

[lgalfaso]

Ok, makes sense

[HAKASHUN]

@pkozlowski-opensource Thanks for your reply.　I've just signed.

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for the commit author(s). If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.

[HAKASHUN]

@googlebot Sorry, I've just added my another email address for CLA.

[pkozlowski-opensource]

@HAKASHUN you need to sign with the exact e-mail you've used to submit your patch

[HAKASHUN]

@pkozlowski-opensource I confirmed the email in the patch. I've signed CLA with the exact email.

[googlebot]

CLAs look good, thanks!