RFR: 8279797: JFR: Show .jfc options in JFR.start help [v2]

[Erik Gahlin]

> Hi,
> 
> Could I have review of an enhancement that shows available .jfc options in the help text for JFR.start. I also fixed a typo. 
> 
> I choose to return an empty string if the default.jfc or profile.jfc can't be parsed. This could potentially happen if a user modifies files in JAVA_HOME/lib/jfr. An alternative would be to return an error message in the help text, but I think it would be hard for users to understand. Likely they think the text describes the command somehow. When they use JFR.start, they will get a parse failure, and it's much more easier to understand at that point.
> 
> This PR has a conflict with https://github.com/openjdk/jdk/pull/7066, so "new JFCModel(s, l -> {});" might need to be changed to "JFCModel.create(s,  l -> {});" before checking in.
> 
> 
> Testing: jdk/jdk/jfr
> 
> Thanks
> Erik

Erik Gahlin has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'openjdk:master' into starthelp
 - Add logging
 - Initial

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7073/files
  - new: https://git.openjdk.java.net/jdk/pull/7073/files/3d99889f..8b088e7e

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7073&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7073&range=00-01

  Stats: 1104 lines in 78 files changed: 757 ins; 142 del; 205 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7073.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7073/head:pull/7073

PR: https://git.openjdk.java.net/jdk/pull/7073