Pull GN Windows binary @ 242181

This is to get the Windows-only change 242978 to write the platform for MSVS GYP files.

R=scottmg@chromium.org
TBR=scottmg@chromium.org

Review URL: https://codereview.chromium.org/120183004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242193 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242193