Finish modules build in GN.

Add some missing targets and do some minor fixes and additions.

Hook up modules and web targets to the build now that they work.

R=jamesr@chromium.org

Review URL: https://codereview.chromium.org/343503003

git-svn-id: svn://svn.chromium.org/blink/trunk@176363 bbb929c8-8fbe-4397-9dbb-9b2b20218538