RFR: 8258754: Gracefully fallback to the OpenGL rendering pipeline if Metal rendering pipeline initialization fails [v9]

[Ajit Ghaisas]

> This implements fallback to the OpenGL rendering pipeline if Metal rendering pipeline initialization fails.
> I have tested this fallback on 10.15.4 by stubbing code. We need real testing on a system where Metal is not available.

Ajit Ghaisas has updated the pull request incrementally with one additional commit since the last revision:

  fix review comment

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Changes:
  - all: https://git.openjdk.java.net/lanai/pull/147/files
  - new: https://git.openjdk.java.net/lanai/pull/147/files/78225469..2600550f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=lanai&pr=147&range=08
 - incr: https://webrevs.openjdk.java.net/?repo=lanai&pr=147&range=07-08

  Stats: 4 lines in 1 file changed: 0 ins; 3 del; 1 mod
  Patch: https://git.openjdk.java.net/lanai/pull/147.diff
  Fetch: git fetch https://git.openjdk.java.net/lanai pull/147/head:pull/147

PR: https://git.openjdk.java.net/lanai/pull/147