GitLab

Move windows implementation to pimpl idiom
  http://c2.com/cgi/wiki?PimplIdiom

There should be no behavior change.

BUG=none
TEST=ConditionVariableTest in base_unittests suffice
Review URL: http://codereview.chromium.org/8823012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@113439 0039d316-1c4b-4281-b951-d872f2087c98