Reenabled ANGLE_instanced_arrays on Windows

Corruption that was occuring has been fixed in https://code.google.com/p/angleproject/issues/detail?id=467, which has been rolled into Chrome.

BUG=288391

Review URL: https://codereview.chromium.org/24672002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225551 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225551