Maintain failedTests list within GMMain object

Maintain failedTests list within GMMain object
Committed: https://code.google.com/p/skia/source/detail?r=6390

[epoger, 2012-11-09 21:29:07]

Ready to review at patchset 4.

I think this is a cleaner way to maintain the failedTests list: rather than
passing ever-more parameters between static functions, empower the GMMain object
to maintain its own state as it goes.

(The addition of all the maxPixelError pointer passing in
https://codereview.appspot.com/6826080/ is what inspired me to do this)

Tested using my new gm self-test from https://codereview.appspot.com/6827068 .

[epoger, 2012-11-12 18:15:16]

tiny, documentation-only change in patchset 6... this is (still) ready for
review.

[reed1, 2012-11-12 21:44:42]

lgtm