RFR: 8279386: Remove duplicate RefProcPhaseTimeTracker

[Albert Mingkun Yang]

Simple change of removing duplicate code.

Test: hotspot_gc

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

Commit messages:
 - RefProcPhaseTimeTracker

Changes: https://git.openjdk.java.net/jdk/pull/6947/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6947&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8279386
  Stats: 24 lines in 3 files changed: 0 ins; 24 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6947.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6947/head:pull/6947

PR: https://git.openjdk.java.net/jdk/pull/6947