8163511: Allocation of compile task fails with assert: "Leaking compilation tasks?" Summary: Use weak handles for compile tasks to allow unloading of referenced methods. Reviewed-by: kvn, coleenp, eosterlund

/build/
/dist/
/.idea/
nbproject/private/
/webrev
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/.jib/
.DS_Store
.metadata/
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test/nashorn/script/external
test/nashorn/lib
NashornProfile.txt
**/JTreport/**
**/JTwork/**