RFR: 8202140: TLAB logging is not correct for G1

[Stefan Johansson]

Hi,

Please review this small change to make TLAB logging more correct, 
especially for collectors using regions.

JBS: https://bugs.openjdk.java.net/browse/JDK-8202140
Webrev: http://cr.openjdk.java.net/~sjohanss/8202140/00/

Summary
The current TLAB logging is not completely correct for G1 and other 
collectors using regions. The logging in 
ThreadLocalAllocBuffer::print_stats() expects that the allocated size is:
size_t alloc = _number_of_refills * _desired_size;

For each region in G1 the last TLAB might be smaller then _desired_size 
and therefor we need to add a separate value to account the actual 
allocated size.

Testing
Verified output to include reasonable values and ran through basic mach5 
testing.

Cheers,
Stefan