Consider making closure_js_test "_test" file suffix configurable

[aproxs]

closure_js_test is checking that the files in srcs end with _test.js: https://github.com/bazelbuild/rules_closure/blob/master/closure/testing/closure_js_test.bzl#L40

Nowadays angular is recommending a naming structure where test files end with .spec.js: https://angular.io/docs/ts/latest/guide/style-guide.html#!#02-10

Besides forcing a naming consistency across the app and the test files (which is a really good thing), is there any other reason to prescribe that test files must end in _test.js?

Would it make sense to make the suffix configurable or more flexible?