Revert of Revert of Change PageTest.WillStartBrowser to depend on platform instead of browser object as it would not ha…

Revert of Revert of Change PageTest.WillStartBrowser to depend on platform instead of browser object as it would not ha… (patchset #1 id:1 of https://codereview.chromium.org/562243004/)

Reason for revert:
Reverting the revert. Bot still failed with this CL reverted. Sorry for the noise.

Original issue's description:
> Revert of Change PageTest.WillStartBrowser to depend on platform instead of browser object as it would not ha… (patchset #1 id:1 of https://codereview.chromium.org/554583003/)
>
> Reason for revert:
> It looks like the moto E perf bots are broken. This change looks like it makes sense so I'm reverting.
>
> crbug.com/414267
>
> Original issue's description:
> > Change PageTest.WillStartBrowser to depend on platform instead of browser object as it would not have been created at this point.
> >
> > BUG=413481
> >
> > Committed: https://crrev.com/9bb65868ce3ac1e5aae3a844beacf62281c332b6
> > Cr-Commit-Position: refs/heads/master@{#294703}
>
> TBR=nduca@chromium.org,nednguyen@google.com,tonyg@chromium.org,chrishenry@google.com,wuhu@google.com
> NOTREECHECKS=true
> NOTRY=true
> BUG=413481
>
> Committed: https://crrev.com/5f712b7be45145522f183d683f11bfb243dd89e1
> Cr-Commit-Position: refs/heads/master@{#294816}

TBR=nduca@chromium.org,nednguyen@google.com,tonyg@chromium.org,chrishenry@google.com,wuhu@google.com
NOTREECHECKS=true
NOTRY=true
BUG=413481
Committed: https://crrev.com/19ec9dafd5f465da381974c78a670b0e5fb15d22
Cr-Commit-Position: refs/heads/master@{#294850}

[dsinclair, 2014-09-15 17:54:50]

Created Revert of Revert of Change PageTest.WillStartBrowser to depend on
platform instead of browser object as it would not ha…