[jdk8u] RFR: 8303828: [Solaris] Broken jdk8u build after JDK-8266391

[Adam Farley]

Because Solaris currently lacks this class, the build breaks when compiling Metrics.java. Inserting a dummy class to fix that.

This takes the same approach as [JDK-8303408](https://bugs.openjdk.org/browse/JDK-8303408), only on Solaris.

This change is being proposed directly to JDK8u because I'm not aware of Solaris platform support post-JDK8.

P.S. This PR is being created for jdk8u (as well as jdk8u-dev) as per this advice [here](https://github.com/openjdk/jdk8u-dev/pull/280#issuecomment-1460740821).

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Commit messages:
 - Fix for build break on Solaris due to missing class

Changes: https://git.openjdk.org/jdk8u/pull/37/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u&pr=37&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8303828
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk8u/pull/37.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u pull/37/head:pull/37

PR: https://git.openjdk.org/jdk8u/pull/37