Mojo JS bindings: simplify mojo.connectToService() usage - Part 1

This is an incremental step towards the goals listed in crbug.com/419160

The Mojo JS bindings now export an object for each interface. The object itemizes the interface values needed at runtime. Here's an example:

  exports.Service = {
    name: 'sample::Service',
    proxyClass: ServiceProxy,
    stubClass: ServiceStub,
    validateRequest: validateServiceRequest,
    validateResponse: null,
  };

I've removed the individual exports of the proxy and stub class names as well as the interface "NAME_" property that was added to proxy and stub classes.

When possible, the object for an interface's client is added.  For example:

  exports.Service.client = exports.ServiceClient;

The next step (next patch) will automatically create a stub client object that delegates to a user supplied object.

BUG=419160

Review URL: https://codereview.chromium.org/628763002

Cr-Commit-Position: refs/heads/master@{#298509}
20 files changed