Ensure a good experience for ARES-6 error reporting

Ensure a good experience for ARES-6 error reporting
https://bugs.webkit.org/show_bug.cgi?id=171699

Reviewed by Filip Pizlo and Jon Davis.

This patch fixes a bug where we would silently fail running ARES-6. The bug
was that we were calling reportError with the wrong |this| value.
I also cleaned up a bit of the code around error reporting. We
now indicate which test failed, and update the status to reflect
that a failure happened.

This patch also modifies the CSS a bit to work better on smaller
screened devices. The CSS prevents the status from having a line
break both when an error is reported and when we're running the
benchmark.

* ARES-6/driver.js:
(Driver):
(Driver.prototype.reportError):
* ARES-6/results.js:
(Results.prototype.reportError):
(Results):
* ARES-6/styles.css:
(.start):
(#status):
(.failed):
(#status.failed):
(.test .failed:before):
(#magic):
(@media only screen and (max-width: 784px)):
(.test):
(p):
(@media only screen and (max-width: 320px)):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@217701 268f45cc-cd09-0410-ab3c-d52691b4dbfc