RFR: 8290017: Directly call HeapRegion::block_start in G1CMObjArrayProcessor::process_slice

[Thomas Schatzl]

Hi all,

  please review this small change to have `G1CMObjArrayProcessor::process_slice` call `HeapRegion::block` directly instead of indirectly via `G1CollectedHeap`. This saves a check and an indirection (but generally isn't perf sensitive anyway, but still).

Testing: tier1-3

Thanks,
  Thomas

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Commit messages:
 - Initial version

Changes: https://git.openjdk.org/jdk/pull/9428/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9428&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8290017
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/9428.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9428/head:pull/9428

PR: https://git.openjdk.org/jdk/pull/9428