RFR: 8275333: Print count in "Too many recored phases?" assert

[Stefan Karlsson]

Just a small change to get some more information when this assert fails.

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Commit messages:
 - 8275333: Print count in "Too many recored phases?" assert

Changes: https://git.openjdk.java.net/jdk/pull/5966/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5966&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275333
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5966.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5966/head:pull/5966

PR: https://git.openjdk.java.net/jdk/pull/5966