RFR: 8261441: JFR: Filename expansion [v8]

[Denghui Dong]

> Hi,
> Could I have a review of this change that let the users could use `%p` in the filename to represent the PID  when JFR.start/stop/dump.
> 
> I haven't implemented `%t` described in the issue, because I don't think it's very useful.
> 
> Best,
> Denghui Dong

Denghui Dong has updated the pull request incrementally with two additional commits since the last revision:

 - update
 - update

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4550/files
  - new: https://git.openjdk.java.net/jdk/pull/4550/files/a9f62c74..07525b3a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4550&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4550&range=06-07

  Stats: 8 lines in 5 files changed: 1 ins; 2 del; 5 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4550.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4550/head:pull/4550

PR: https://git.openjdk.java.net/jdk/pull/4550