GitLab

Implementation of the NetworkingConfigService and boiler plate code for the
networking.config API.

Reviewers:
Please see
1) https://docs.google.com/document/d/1V8YGouKC477iC11L4PL8H_HU1Ru3R5kMhXppuoIVNeo for the design document.
2) https://docs.google.com/drawings/d/12Hai1LdaPzwtkrQUdCjSpt1s7InRNNBDeWiW5ujfIRg for a flow diagram.

Review URL: https://codereview.chromium.org/880073002

Cr-Commit-Position: refs/heads/master@{#314303}