Split condition_variable_win.cc into native (for Vista and newer OS versions) and generic implementation (based on events).

Note that this means that there is no new code. The code has been taken directly from condition_variable_win.cc/h compensating minimally to be able to split up the two code paths.

Tested by:
1) Disabling native implementation and send to try bots.
2) Only return native implementation (i.e. if native implementation returns NULL there will be a crash when using the condition variable) and send to try bots.
3) The final cl sent to trybots.
All tests pass.

The changes are due to static analyzer code complaints.

BUG=N/A

Review URL: https://webrtc-codereview.appspot.com/1191004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@3728 4adac7df-926f-26a2-2b94-8c16560cd09d
9 files changed