RFR: 8273369: Computing micros between two instants unexpectedly overflows for some cases [v2]

[Naoto Sato]

> Please review the fix to the issue. Avoiding overflow by not calling nanosUntil() directly, which will overflow beyond Long.MAX_VALUE difference in nano unit.

Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:

  Added a constant for nanos per micro.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5396/files
  - new: https://git.openjdk.java.net/jdk/pull/5396/files/09d9b257..4b874ff6

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5396&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5396&range=00-01

  Stats: 5 lines in 1 file changed: 4 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5396.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5396/head:pull/5396

PR: https://git.openjdk.java.net/jdk/pull/5396