Delegate time zone names handling to ICU in SDF.

Delegate parsing and formatting time zone names to the relevant ICU code
(android.icu.text.TimeZoneNames).

This fixes an issue where the cache of time zone names was time dependent.

The old code that uses DateFormatSymbols.getZoneStrings() for parsing
and formatting is still used  as a fallback, but it's only used if the
DateFormatSymbols.setZoneStrings() has been called explicitly.

Performance of this code is between ~40-105% of the old code, depending
on the exact use case (Measured with SimpleDateFormatBenchmark, times in
ns per iteration on a bullhead, with cpu frequencies locked to 864000):

                                        Before   After
time_createAndParseWithTimeZoneLong    105,195  172,892
time_createAndParseWithTimeZoneShort    96,313  189,077
time_createFormatWithTimeZone           26,551   25,351
time_formatWithTimeZoneLong             10,700   13,151
time_formatWithTimeZoneShort            10,872   13,352
time_parseWithTimeZoneLong              57,348  101,426
time_parseWithTimeZoneShort             48,323  114,452
time_parseWithoutTimeZone               15,293   16,128

This change slightly affects how time zone names are parsed and
formatted:

* When formatting a date, we now use time zone name information that is
  accurate for the time we format. Previously we implicitly used the time
  at which the time zone name data was cached (which happened to be
  whatever the RTC was at boot time for the root, US and default locale).
  While this may result in differences in how past dates are formatted
  (specifically when formatting a date that is before the last time a time
  zone name changed), the new behaviour is definitely more correct than the
  old one.
* When parsing a date, we now use the time zone name information that is
  accurate at time the parse happens (according to the RTC). This means that
  some older dates might not round-trip correctly (because the zone name
  information used for parsing and formatting is different). Previously we
  used the same time as for formatting (i.e. some arbitrary time when the
  zone names were cached).

Test: libcore/run-libcore-tests libcore.java.text org.apache.harmony.tests.java.text
Bug: 20879084
Change-Id: Id9f70acad60d97b9879df14b5b5de6e89b209de3

0 files changed, 0 insertions, 0 deletions