Reenable PnaclHeaderTest, set up observer before navigating.

Reenable PnaclHeaderTest, set up observer before navigating.

Hopefully setting up the observer before loading the HTML will fix the flake.
Not sure why I set things up in other order before =(

In the test-fail logs, it looks like none of the Log events
from JS are making it back to the test harness to print,
but they are making it to the JS console. So, I'm assuming
this is a sign that the observer isn't set up in time.

BUG=315328
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=235824

[jvoung (off chromium), 2013-11-11 19:10:34]

ping

[jvoung (off chromium), 2013-11-15 17:15:58]

ping

[Nick Bray (chromium), 2013-11-16 00:14:18]

LGTM

[commit-bot: I haz the power, 2013-11-18 19:25:20]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jvoung@chromium.org/63433002/1

[commit-bot: I haz the power, 2013-11-18 21:52:41]

Change committed as 235824