RFR: 8276298: G1: Fix or remove G1SegmentedArrayBufferList::add

[Hamlin Li]

This is minor removal of unused method G1SegmentedArrayBufferList::add.

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Commit messages:
 - Merge branch 'openjdk:master' into remove-G1SegmentedArrayBufferList-add
 - Initial commit

Changes: https://git.openjdk.java.net/jdk/pull/6224/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6224&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8276298
  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6224.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6224/head:pull/6224

PR: https://git.openjdk.java.net/jdk/pull/6224