Remove DateFormat time pattern caching

This change removes pattern string caching from
the SimpleDateFormat constructor only used by
DateFormat.getInstance().

Before this change, the LocaleData.getTimeFormat(int) method
that is used to populate the cached data can return different
information for SHORT and MEDIUM times based on the
DateFormat.is24Hour setting and so the results are not safe
to cache: if the user modifies their "use 24-hour format"
setting and the data is already cached the old pattern was
persisted forever.

This was also causing various CTS tests to fail if the device
had the "use 24-hour format" setting on. For example:

libcore.java.text.OldDateFormatTest
org.apache.harmony.tests.java.text.MessageFormatTest
org.apache.harmony.tests.java.util.DateTest

Callers of java.text.DateFormat.get(int, int, int, Locale)
are affected. In practice that means DateFormat.getTimeInstance()
/ getTimeInstance(int) and getTimeInstance(int, Locale).

Indirect callers in the Android framework include:
android.text.format.DateUtils
android.text.format.DateFormat
android.widget.DigitalClock
java.text.MessageFormat

This change has a small negative affect on performance, but
not a significant one: obtaining a DateFormat via
DateFormat.getTimeInstance() goes from ~28us to
~33us on an Angler device.

Full results for the benchmarks included:

Before:

benchmarkMethod=timeGetDateTimeInstance
runtime(ns): min=27518.68, 1st qu.=28461.12, median=28775.87,
mean=28732.44, 3rd qu.=29235.59, max=29320.80
runtime(ns): min=28599.17, 1st qu.=28769.57, median=29277.13,
mean=29682.69, 3rd qu.=29824.08, max=33419.06

benchmarkMethod=timeGetDateTimeInstance_multiple
runtime(ns): min=108667.38, 1st qu.=110223.70, median=111547.98,
mean=112173.89, 3rd qu.=113748.88, max=118091.12
runtime(ns): min=102995.66, 1st qu.=105045.16, median=108558.77,
mean=108817.18, 3rd qu.=111677.65, max=115886.11

After:

benchmarkMethod=timeGetDateTimeInstance
runtime(ns): min=31365.39, 1st qu.=32904.01, median=33303.47,
mean=33244.55, 3rd qu.=33983.32, max=34052.99
runtime(ns): min=31785.28, 1st qu.=32921.68, median=33364.01,
mean=33531.03, 3rd qu.=34301.06, max=35031.33

benchmarkMethod=timeGetDateTimeInstance_multiple
runtime(ns): min=126834.48, 1st qu.=128605.17, median=130069.44,
mean=131157.63, 3rd qu.=134095.26, max=138164.92
runtime(ns): min=124618.08, 1st qu.=126097.91, median=130190.93,
mean=130027.17, 3rd qu.=131991.56, max=140283.06

Bug: 31762542
Test: Ran CtsLibcoreTestCases with the "use 24-hour format" on
      and off
Change-Id: I02798e8fcd2ed5f7625a32261112560b5d9b18f3

0 files changed, 0 insertions, 0 deletions