Add a callback to cleanup TLS data on Windows.

Add a test to ensure that it works.

BUG: http://code.google.com/p/skia/issues/detail?id=939

Review URL: https://codereview.appspot.com/6785045

git-svn-id: http://skia.googlecode.com/svn/trunk@6126 2bbb7eff-a529-9590-31e7-b0007b416f81
2 files changed