RFR: 8256580: Fault in new grid display

[Hannes Wallnöfer]

This change makes sure empty cells in summary tables are not dropped, which was the case when the `-nocomment` option was used. 

It also adds tests to check summary table contents both in normal operation and with `-nocomment` option.

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Commit messages:
 - JDK-8256580: Fault in new grid display

Changes: https://git.openjdk.java.net/jdk/pull/1438/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1438&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256580
  Stats: 313 lines in 3 files changed: 311 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1438.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1438/head:pull/1438

PR: https://git.openjdk.java.net/jdk/pull/1438