RFR: 8264908: Investigate adding BOT range check in G1BlockOffsetTablePart::block_at_or_preceding [v2]

[Ivan Walulya]

> Hi all,
> 
> Please review this cleanup change to add an assert to G1BlockOffsetTablePart::block_at_or_preceding. Additionally, remove code that attempts to read beyond the _next_offset_index threshold. 
> 
> Testing: Tier 1-3

Ivan Walulya has updated the pull request incrementally with one additional commit since the last revision:

  @albert suggested changes

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4775/files
  - new: https://git.openjdk.java.net/jdk/pull/4775/files/ea6c0c3c..96ff7958

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4775&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4775&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4775.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4775/head:pull/4775

PR: https://git.openjdk.java.net/jdk/pull/4775