linux_aura: Turn aura on on the main linux builders.

This is essentially a revert of r227214. In the interim, we've enabled interactive_ui_tests, switched to openbox on the bots to theoretically fix browser_tests, and have a speculative nacl integration crash fix.

BUG=125106,303342,304554,125106,304555,316716,316919

Review URL: https://codereview.chromium.org/26622003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@234139 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 234139