Use Interlocked calls in win32 once() implementation.

This is simpler than the previous scheme, which tried to allocate
the CRITICAL_SECTION struct in a thread-safe manner before it
could use it to run the wrapped function in a thread-safe manner.

Change-Id: I172e5544e5f16403a3a0e5e2b9104b1292a0d786
1 file changed