This way the Closure Compiler needs to be run 693 fewer times.

    $ bazel query 'kind(closure_js_library, deps(//js/closure/...))' | wc -l
    802  # <-- before
    109  # <-- after

Notes:

1. These build rules export the world, for the sake of convenience:

- @io_bazel_rules_closure//closure/library
- @io_bazel_rules_closure//closure/library:testing

2. closure_js_library has an implicit dependency on base.js.

3. rules_closure runs jscomp on each closure_js_library.