GitLab

This target was initially defined in mojo_public.gypi, but
it depends on code outside of mojo/public. Move it to
mojo.gyp, where the target for code in the adjacent directory
(mojo/bindings/js) is defined.

BUG=None
TEST=trybots

Review URL: https://codereview.chromium.org/403803003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284405 0039d316-1c4b-4281-b951-d872f2087c98