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

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}

[wuhu, 2014-09-12 20:54:09]

wuhu@google.com changed reviewers:
+ chrishenry@google.com, nduca@chromium.org, nednguyen@google.com,
tonyg@chromium.org

[wuhu, 2014-09-12 20:54:09]

Please review when you have time

[nednguyen, 2014-09-12 21:04:31]

On 2014/09/12 20:54:09, wuhu wrote:
> Please review when you have time

LGTM

[nednguyen, 2014-09-12 21:04:46]

The CQ bit was checked by nednguyen@google.com

[commit-bot: I haz the power, 2014-09-12 21:12:19]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/554583003/1

[wuhu, 2014-09-12 21:15:22]

Patchset #2 (id:20001) has been deleted

[nednguyen, 2014-09-12 23:20:32]

The CQ bit was checked by nednguyen@google.com

[commit-bot: I haz the power, 2014-09-12 23:22:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/554583003/1

[commit-bot: I haz the power, 2014-09-13 00:36:01]

Committed patchset #1 (id:1) as 20f6dc3389463e542dac2295348d41160b99daca

[commit-bot: I haz the power, 2014-09-13 00:47:42]

Patchset 1 (id:??) landed as
https://crrev.com/9bb65868ce3ac1e5aae3a844beacf62281c332b6
Cr-Commit-Position: refs/heads/master@{#294703}

[dsinclair, 2014-09-15 13:52:27]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/562243004/ by dsinclair@chromium.org.

The reason for reverting is: It looks like the moto E perf bots are broken. This
change looks like it makes sense so I'm reverting.

crbug.com/414267.