RFR: 8257186: Size of heap segments is not computed correctlyFix overflow in size computation for heap segments

[Maurizio Cimadamore]

There is a subtle bug in the heap segment factories: the byte size is computed using an int multiplication instead of a long multiplication. Because of that, it is possible to observe overflow when creating segments out of arrays whose carrier has a byte size greater than one.

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Commit messages:
 - Fix overflow in size computation for heap segments

Changes: https://git.openjdk.java.net/jdk/pull/1466/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1466&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257186
  Stats: 29 lines in 2 files changed: 21 ins; 0 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1466.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1466/head:pull/1466

PR: https://git.openjdk.java.net/jdk/pull/1466