Cover JapaneseChronology with tests.

Cover dateEpochDay method.

Bug: 182165762
Test: atest libcore.java.time.chrono.JapaneseChronologyTest
Change-Id: I216257d767413506d2635794e6925683d86d5e7a
Merged-In: I216257d767413506d2635794e6925683d86d5e7a
(cherry picked from commit 469e077a51f20fd71a0080d67a86fde6fbf19b6b)
1 file changed