GN: Start of //third_party/WebKit/Source/web

The make_file_arrays template should probably go in Source/build/ since it
is also used in modules and on mac I'm getting override errors in clang,
but this is a start. Most things compile.

R=brettw@chromium.org

Review URL: https://codereview.chromium.org/337703003

git-svn-id: svn://svn.chromium.org/blink/trunk@176346 bbb929c8-8fbe-4397-9dbb-9b2b20218538