Fix selenium to detect and handle browser crashes.

Fix selenium to detect and handle browser crashes.

Some context:
On windows, selenium will be hanging a chrome browser
crashes and additional to this we would actually not get information
that the browser crashed, we would get this as a failing test.

This change basically sets up a python timer that will trigger us to
close the browser using browser.service.stop() (I suspect that when
the browser crashes and does not respond in time selenium will call
browser.quit which will be blocking on trying to kill the remote
service).

In addition, this changes the test_runner to handle a crash exitcode
correctly (we will set it to -10 in the bacth runner, I don't know
why, but I dont want to change that in this cl). The current
hasCrashed getter will mask out errors that it does not recognize as
valid windows crashes (of which -10 is not one since it will have a
bunch of set bits in the middle of the bit pattern). I changed this to
explictily recognize the -10 value.
Input on why we have that value is welcome
Committed: https://code.google.com/p/dart/source/detail?r=17752

[kustermann, 2013-01-23 14:12:00]

lgtm

[Emily Fortuna, 2013-01-23 19:05:52]

lgtm