ProfilerPCTickThreshold was left unused by removal of flat profiler in JDK 10.

diff -r 0a48b128e3d4 src/hotspot/share/runtime/globals.hpp
--- a/src/hotspot/share/runtime/globals.hpp Fri Jan 18 16:49:35 2019 +0100
+++ b/src/hotspot/share/runtime/globals.hpp Fri Jan 18 17:07:38 2019 +0100
@@ -1670,9 +1670,6 @@
   develop(intx, DontYieldALotInterval, 10, \
           "Interval between which yields will be dropped (milliseconds)") \
                                                                             \
- develop(intx, ProfilerPCTickThreshold, 15, \
- "Number of ticks in a PC buckets to be a hotspot") \
- \
   notproduct(intx, DeoptimizeALotInterval, 5, \
           "Number of exits until DeoptimizeALot kicks in") \
                                                                             \