<AWT Dev> RFR: 8263363: Minor cleanup of Lanai code - unused code removal and comments correction [v4]

[Ajit Ghaisas]

> Refer JBS for 3 issues that this PR addresses.
> In addition, I have corrected an erroneous free() call in the same method I was cleaning up.

Ajit Ghaisas has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - cleanup MTLContext.invalidateCurrentContext()
 - Merge branch 'master' into cleanup_fix
 - log message correction
 - Review fixes
 - 8263363 - cleanup

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3357/files
  - new: https://git.openjdk.java.net/jdk/pull/3357/files/45e7aec0..746d791d

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3357&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3357&range=02-03

  Stats: 130385 lines in 2601 files changed: 69070 ins; 53454 del; 7861 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3357.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3357/head:pull/3357

PR: https://git.openjdk.java.net/jdk/pull/3357