JMC-4645: Size Distribution charts for I/O pages

[Ken Dobson]

Hi all,

I have a patch that adds charts to the File and Socket I/O pages that
provide the distribution of I/O events by size for
https://bugs.openjdk.java.net/projects/JMC/issues/JMC-4645 .

It currently has one issue with adding to the selection store. Currently I
can only store either *_BYTES_WRITTEN or *_BYTES_READ but not both, it
seems as if we would ideally need some sort of JfrAttributes.SIZE to
address this but I'm not sure how to go about that or whether that's
possible. This issue can be found at SocketIOPage.java:286 and
FileIOPage.java:389. If anybody has any suggestions regarding how to deal
with it that would be great.

The patch can be found here:
http://cr.openjdk.java.net/~kdobson/JMC-4645/webrev/

Thanks,

Ken Dobson