RFR(S): 8215284: Reduce noise induced by periodic task getFileSize()

[Markus Gronlund]

Greetings,

Can I get a review for the following:

Bug: https://bugs.openjdk.java.net/browse/JDK-8215284 
Webrev: http://cr.openjdk.java.net/~mgronlun/8215284/webrev01/ 

Summary: The periodic task operation runs in Java checking the file size of the current chunk. This produces unnecessary exposure and noise by the JFR framework itself. It is especially interesting that the path to check the size of a file produces a memory allocation trace....most likely some effect of autoboxing and lambda constructions...

We can avoid this by diving into the VM instead to test for the rotateDisk condition since the amount written to the current chunk is already tracked there.

Testing: jdk_jfr

Thanks
Markus