Request for Review - 8152208: Summary for phase times are incorrect with and without UseDynamicNumberOfGCThreads

[Jon Masamitsu]

The averages reported for phase times (for example "Ext Root Scanning") were
incorrect.  Not all the per thread values were included in the sum and the
average value was incorrect (this with build 9-ea+1100)

[0.366s][debug][gc,phases            ] GC(2)     Ext Root Scanning 
(ms):   Min:  0.3, Avg:  0.2, Max:  0.4, Diff:  0.0, Sum:  0.3
[0.366s][trace][gc,phases,task       ] 
GC(2)                                0.4  0.3

With the fix all values are included in the sum and the average is correct.

[2.830s][debug][gc,phases            ] GC(0)     Ext Root Scanning 
(ms):   Min:  5.7, Avg:  7.3, Max:  8.9, Diff:  3.1, Sum: 14.6
[2.830s][trace][gc,phases,task       ] 
GC(0)                                8.9  5.7

https://bugs.openjdk.java.net/browse/JDK-8152208
http://cr.openjdk.java.net/~jmasa/8152208/webrev.00/

Thanks.

Jon