RFR: 8268952: Automatically update heap sizes in G1MonitoringScope

[Thomas Schatzl]

Hi,

  can I have reviews to factor out the call to `G1MonitoringScope::update_sizes()` into the destructor of that class? Currently all users seem to call this manually close to the end of the scope `G1MonitoringScope` is in.

Testing: tier1-5

Thanks,
  Thomas

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

Commit messages:
 - Initial version

Changes: https://git.openjdk.java.net/jdk/pull/4529/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4529&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8268952
  Stats: 18 lines in 4 files changed: 7 ins; 11 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4529.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4529/head:pull/4529

PR: https://git.openjdk.java.net/jdk/pull/4529