RFR: 8284697: Avoid parsing the doc comment of an element that is not documented

[Pavel Rappo]

We shouldn't parse comments that are going to be thrown away.

Although the change is simple, I have no idea on how to test it. So I'm tempted to affix the "noreg-other" or "noreg-hard" label on the JBS issue.

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

Commit messages:
 - Reorder checks

Changes: https://git.openjdk.java.net/jdk/pull/8266/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8266&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284697
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8266.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8266/head:pull/8266

PR: https://git.openjdk.java.net/jdk/pull/8266