Make skdiff use enumeration of result types instead of separate booleans for each result type.
Make skdiff use enumeration of result types instead of separate booleans for each result type.

This is one step on the way to a more robust version of skdiff that we can use to address http://code.google.com/p/skia/issues/detail?id=473 ('PDF gradtext gm image results are nondeterministic')

I have confirmed that skdiff results will not change, using tools/tests/run.sh.
Review URL: https://codereview.appspot.com/6208063

csulmone/skia,csulmone/skia,csulmone/skia,csulmone/skia