Add {Will,Did}StartBrowser to record_wpr

Add {Will,Did}StartBrowser to record_wpr.

Needed for PageMeasurements that assume a self._power_metric is created during the WillStartBrowser step.

BUG=

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=286744

[tonyg, 2014-07-29 21:26:31]

lgtm

But I do wonder whether a unittest would help this from accidentally breaking
due to a refactor.

[dtu, 2014-07-29 22:21:27]

lgtm

[ariblue, 2014-07-29 22:38:07]

On 2014/07/29 21:26:31, tonyg wrote:
> lgtm
> 
> But I do wonder whether a unittest would help this from accidentally breaking
> due to a refactor.

Added unittest to check for calls to the added functions, plus ensured that the
--browser gets passed through to those tests. (And other lint fixes). PTAL.

[ariblue, 2014-07-30 18:53:13]

The CQ bit was checked by ariblue@google.com

[commit-bot: I haz the power, 2014-07-30 18:53:56]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/ariblue@google.com/427093002/60001

[ariblue, 2014-07-30 18:54:18]

On 2014/07/30 18:53:13, ariblue wrote:
> The CQ bit was checked by mailto:ariblue@google.com

Got rid of the broken --browser stuff and just kept the new unittests. So
kicking of the commit process.

[commit-bot: I haz the power, 2014-07-31 01:05:25]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_dbg_triggered_tests on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_dbg_tri...)

[commit-bot: I haz the power, 2014-07-31 11:54:45]

Change committed as 286744

[pneubeck (no reviews), 2014-07-31 13:39:43]

A revert of this CL has been created in
https://codereview.chromium.org/437543002/ by pneubeck@chromium.org.

The reason for reverting is: Broke telemetry unittests.

http://build.chromium.org/p/chromium.linux/builders/Linux%20Tests/builds/1260....