RFR 8020040: Improve and generalize the F/J tasks to handle right or left-balanced trees

[Paul Sandoz]

Hi,

This patch, contributed by Doug Lea, improves stream resource management of F/J tasks when processing right-balanced (or more accurately right-heavy) trees (e.g. those created from sequential sources):

  http://cr.openjdk.java.net/~psandoz/tl/JDK-8020040-tasks/webrev/

It took us a while but the end result is remarkably simple: alternate the forking of left and right tasks.

Large or infinite stream sources hooked up a short-circuiting operation such as limit no longer consume ridiculous amounts of memory.

This patch is related to a previous one Henry sent for review (remove catching of OOMEs for splterators from sequential sources)

Paul.