RFR: 8282878: Removed _JavaThread from PhaseTraceTime

[Aleksey Shipilev]

On Wed, 9 Mar 2022 11:49:42 GMT, Alex Blewitt <duke at openjdk.java.net> wrote:

> The `PhaseTraceTime` class has a private `JavaThread _thread` field which doesn't appear to be referenced anywhere, and builds fine without it. It's not clear if this can be removed but it builds cleanly when not present.

The history for this code predates OpenJDK, but I think this field is safe to remove.

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

Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/7756