- Partially implement getThreadUserTime() using getrusage(2). Note we can
only get usage for the current thread. Return -1 if the requested function
is not supported, i.e., user time for other threads, rather than crash. [1]
- Properly implement os::elapsedVTime() using getrusage(). Basically, it is
taken from Linux version.
- Temporarily revert r403748 to fix bootstrapping with earlier OpenJDK8. [2]