Rebaseline date format related tests on Mavericks

The OS X API used by datetime formatter relies on ICU/CLDR underneath.
In English locale, a comma is now present between date and time.

This CL does what the following two CLs did for Linux

https://codereview.chromium.org/302323004
https://codereview.chromium.org/403393004

except that the following test was already revised to work regardless of
the presence of a comma between date and time by the first CL of the two
above and is already passing :

fast/forms/datetimelocal-multiple-fields/datetimelocal-multiple-fields-mouse-events.html

The following two tests need rebaselining because Mavericks now has a
comma between date and timein English locale. These new expected results
are identical to the corresponding Linux results.

fast/forms/datetimelocal-multiple-fields/datetimelocal-multiple-fields-value-set-empty.html
fast/forms/datetimelocal-multiple-fields/datetimelocal-multiple-fields-preserve-value-after-history-back.html

Besides, the generic results for the above two tests are copied to
platform/mac-mountainlion.

BUG=314947
TEST=The above 3 tests pass on Mavericks.

Review URL: https://codereview.chromium.org/418683002

git-svn-id: svn://svn.chromium.org/blink/trunk@178816 bbb929c8-8fbe-4397-9dbb-9b2b20218538