Fix bug in pyauto perf tests where list containing result 0 isn't handled properly.

Fix bug in pyauto perf tests where list containing result 0 isn't handled properly.

Previously, 2 conditions in the code verified an appropriate perf result value
in a list by implicitly converting that value to a boolean.  As a result,
a list value of 0 would be assumed to be invalid, when in fact a perf result
value of 0 may be appropriate.  This CL changes the logic of these conditions
by comparing the list value to None.  That way, even a list value of 0 will
still be considered an appropriate value.

BUG=None
TEST=Ran test perf.YoutubePerfTest on a local ChromeOS device, which
fails without this change, but passes with it.
NOTRY=true


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=141703

[dennis_jeffrey, 2012-06-11 23:00:24]

This CL should fix perf.YoutubePerfTest.testYoutubeDroppedFrames, which
currently fails on ChromeOS.

[tonyg, 2012-06-12 19:14:21]

lgtm

[commit-bot: I haz the power, 2012-06-12 19:15:53]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dennisjeffrey@chromium.org/10537111/1

[commit-bot: I haz the power, 2012-06-12 19:16:33]

Change committed as 141703