RFR(XXS): 8203457: Add back missing full buffer notification

[Claes Redestad]

Markus,

On 2018-05-21 10:44, Markus Gronlund wrote:
> On a full global buffer, the notification is never sent to the recorder thread for it to flush to disk. This means the in-memory buffer system fills up until eventually no free space is left. At this point threads will start to discard data and write "data loss" events.
>
> Need to add back the missing notification.
>
> Bug:https://bugs.openjdk.java.net/browse/JDK-8203457
>
> Webrev:http://cr.openjdk.java.net/~mgronlun/8203457/webrev00/

thanks for fixing this! Fix looks good, and the cleanups in the 
neighbourhood seems reasonable, too.

Nit: Could the "mutexed" accesses assert that we're actually holding the 
mutex we think we are? No need for a re-review if you choose to fix this.

/Claes