Reland of lemetry: Fix startup benchmarks so that all metrics get recorded.

Reland of lemetry: Fix startup benchmarks so that all metrics get recorded. (patchset #2 id:70001 of https://codereview.chromium.org/1438533003/ )

Reason for revert:
Looks like my changes were still required to get the metric:

foreground_tab_request_start

https://code.google.com/p/chromium/issues/detail?id=560760&q=owner%3Aerikchen%40chromium.org&sort=-modified&colspec=ID%20Pri%20M%20Iteration%20ReleaseBlock%20Cr%20Status%20Owner%20Summary%20OS%20Modified

Original issue's description:
> Revert of telemetry: Fix startup benchmarks so that all metrics get recorded.
>
> Reason for revert:
> Theoretically, these changes should no longer be required, now that
> https://code.google.com/p/chromium/issues/detail?id=529340#c7 has landed.
>
> Original issue's description:
> > telemetry: Fix startup benchmarks so that all metrics get recorded.
> >
> > *PERF SHERRIF: if startup benchmarks become red, this CL is to be reverted.
> >
> > The lack of a page navigation was preventing the metric
> > Startup.FirstWebContents.NonEmptyPaint from being emitted. The addition of the
> > RAF logic check is to prevent theoretical race conditions - it may be overkill.
> >
> > BUG=513364
> > CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_perf_bisect;tryserver.chromium.perf:android_nexus5_perf_bisect
> >
> > Committed: https://crrev.com/0bc400e1c96da5a05379bc1b634ec278f36d3417
> > Cr-Commit-Position: refs/heads/master@{#347402}
>
> TBR=nednguyen@google.com
> BUG=513364
> CQ_EXTRA_TRYBOTS=tryserver.chromium.perf:linux_perf_bisect;tryserver.chromium.perf:mac_10_10_perf_bisect;tryserver.chromium.perf:win_perf_bisect;tryserver.chromium.perf:android_nexus5_perf_bisect
>
> Committed: https://crrev.com/359e8b1514eba38cb34d72443c223f49d1a55656
> Cr-Commit-Position: refs/heads/master@{#359024}

TBR=nednguyen@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=513364
Committed: https://crrev.com/df3cbbfc4c84ec3405ab30a921dbdc2d320c3b20
Cr-Commit-Position: refs/heads/master@{#361404}

[erikchen, 2015-11-24 18:51:04]

Created Reland of lemetry: Fix startup benchmarks so that all metrics get
recorded.

[commit-bot: I haz the power, 2015-11-24 18:52:02]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1475773003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1475773003/1

[commit-bot: I haz the power, 2015-11-24 18:55:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-24 18:56:29]

Patchset 1 (id:??) landed as
https://crrev.com/df3cbbfc4c84ec3405ab30a921dbdc2d320c3b20
Cr-Commit-Position: refs/heads/master@{#361404}