Import json by default, then simplejson.

Import json by default, then simplejson.

Since json is included in Python 2.6 and above,
first try importing it, then import simplejson
if that fails.

Also ensure that any unicode characters are converted to
ASCII before checksumming to avoid checksum differences
in strings generated by json and simplejson modules.

TEST=make_expectations.py runs on Windows using the
stock Python in depot_tools

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=82946

[nsylvain, 2011-04-25 22:59:36]

LGTM

[cmp, 2011-04-25 23:21:13]

Patch updated, PT another L.

[nsylvain, 2011-04-25 23:29:01]

lgtm