Add JapaneseDate tests.

Cover JapaneseDate.minus with tests.

Bug: 182165762
Test: atest libcore.java.time.chrono.JapaneseDateTest

(cherry picked from commit 20015a0a502a297b3d0aa7cbf75585ef7106bd81)

Change-Id: I895a00d3ceb2d1e969e89d3b975e13be778f5de8
Merged-In: I895a00d3ceb2d1e969e89d3b975e13be778f5de8
1 file changed