RFR: 8246788: ZoneRules invariants can be broken

[Stuart Marks]

Tighten up argument checking in constructor.

-------------

Commit messages:
 - 8246788: ZoneRules invariants can be broken

Changes: https://git.openjdk.java.net/jdk/pull/2191/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2191&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8246788
  Stats: 90 lines in 2 files changed: 87 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2191.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2191/head:pull/2191

PR: https://git.openjdk.java.net/jdk/pull/2191