Apparently because of its use of a custom SecurityManager, the nio CheckPermissions test causes
infinite recursion and eventually a StackOverflowError when run with -Xcomp.

% b40/fastdebug/bin/java -server -XX:-TieredCompilation -Xcomp -XX:+TraceExceptions -cp classes/ CheckPermissions >& L
% egrep StackOverflowError L | wc
     14 146 1799

This problem showed up previously with C1, and something in C1 was fixed, but the problem still shows up with C2, and test has not been fixed. We should check if the test is making bad assumptions about class loading, or if -Xcomp is changing the semantics. In other words, even if the test passes, the infinite recursion causes the test to run longer than necessary, and could be causing it to short-circuit some checks.