[jdk8u-dev] RFR: 8316328: Test jdk/jfr/event/oldobject/TestSanityDefault.java times out for some heap sizes

[SendaoYan]

Hi all,
  This is clean backport of [JDK-8316328](https://bugs.openjdk.org/browse/JDK-8316328), which try to limit the memory used by the test, avoid timeout failure with some jvm options or on some specific enviroments. Only change the testcase, no risk.

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Commit messages:
 - Backport 9b1d6d66b8297d53c6b96b9e2f9bd69af90ab8fb

Changes: https://git.openjdk.org/jdk8u-dev/pull/505/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=505&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316328
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/505.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/505/head:pull/505

PR: https://git.openjdk.org/jdk8u-dev/pull/505