fix: use well-formatted URLs when setting breakpoints

[kjin]

Newer versions of Node will require that URLs be well-formatted when setting breakpoints (and will also return well-formatted URLs), as a result of nodejs/node#22223 (this will also affect versions of Node to which that PR will be backported). Enforcing well-formatted URLs will break the Debug Agent, so this PR addresses that.

If tests pass for current versions of Node, I think this should be merged now (rather than wait for Node 11).

• Tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)

[JustinBeckwith]

@kjin @googleapis/node-team this is just kinda hangin around :) Who should be reviewing this?

[soldair]

seems good.
is there a way to add a test for this?

[DominicKramer]

Thanks for addressing this. Looks good once the tests are passing. I agree it would be nice if there was a way to test this.

[kjin]

@JustinBeckwith This PR needs work, I've been busy with other things so haven't had a chance to update it.

@soldair @DominicKramer Currently, many tests will fail on Node master (or v10.x-staging) without this change... not sure if we need to explicitly test this.

[kjin]

@soldair @DominicKramer I'd appreciate a look on the newest commit. Thanks!

[DominicKramer]

@kjin I've updated this PR to merge your approach and the approach I took in PR #560. Could you take a look to see if it looks good to land? Thanks.

[ofrobots]

Your change LGTM. If the tests are good, go ahead and land this.

[DominicKramer]

@ofrobots Ok will do.

[DominicKramer]

This will be able to land after PR #583 lands.