Factor out some common logic from the launchers.

Factor out some common logic from the launchers.

This also ensures that a launcher that fails after being closed doesn't
break anything.

R=kevmoo@google.com

Committed: https://github.com/dart-lang/test/commit/97c3ad2e81dc5948a8b82fbc986df2b320af2da0

[kevmoo, 2015-06-11 09:31:11]

On 2015/06/11 00:58:42, nweiz wrote:

I don't have time to review the code – yet

But running the tests I found this – a regression

00:06 +255 -1: test/runner/browser/content_shell_test.dart: reports an error in
onExit
  Expected: throws a ApplicationException with message a string starting with
'Failed to run content shell: No such file or directory'
    Actual: <Closure: () => dynamic>
     Which: threw ApplicationException:<Failed to run Content Shell: No such
file or directory
    Command: _does_not_exist --dump-render-tree http://dart-lang.org.>
  Actual exception trace:
    package:test                                       
ContentShell.ContentShell
    test/runner/browser/content_shell_test.dart 150:28  main.<fn>


  package:test                                       expect
  test/runner/browser/content_shell_test.dart 152:5  main.<fn>

[kevmoo, 2015-06-15 22:59:55]

lgtm

[nweiz, 2015-06-15 23:09:27]

Committed patchset #2 (id:20001) manually as
97c3ad2e81dc5948a8b82fbc986df2b320af2da0 (presubmit successful).