RFR: 8155087: Calcualtion in other_time_ms() is incorrect

[Stefan Johansson]

Hi,

Please review this small fix for:
https://bugs.openjdk.java.net/browse/JDK-8155087

Webrev:
http://cr.openjdk.java.net/~sjohanss/8155087/hotspot.00/

Summary:
The calculation in other_time_ms() used the average time of some known 
parallel phases to calculate the "other" time. In the past this might 
have been the best way to do it but now we actually measure the parallel 
time and can use this instead.

Testing:
* RBT with 
hotspot/test/:hotspot_jprt,vm.parallel_class_loading.testlist,jdk/test/:tier1,vm.gc.testlist

Thanks,
Stefan