RFR(XXS) 8203635: JFR sampler thread does not record stack info

[Zhengyu Gu]

Please review this trivial change that added 
record_stack_base_and_size() call to JFR sampler thread, so NMT can 
count it correctly.

Bug: https://bugs.openjdk.java.net/browse/JDK-8203635
Webrev: http://cr.openjdk.java.net/~zgu/8203635/webrev.00/

Test:
   tier1_runtime on Linux 64

Thanks,

-Zhengyu