client: don't call callbacks if close() is called

[virtuald]

• This could break some existing clients using the raw grpc API (maybe should document it?), but ts-protoc-gen clears out the callbacks anyways so this shouldn't cause anyone pain
• Fixes race condition on stream close #257

... I'd write a test for this, but I'm not actually a Javascript/Typescript developer so I'm not familiar with the test framework.

[virtuald]

Worth noting that when I built this PR into my application, the errors I was experiencing went away.

[johanbrandhorst]

This seems reasonable to me, but I'm also not a typescript developer 😂. I've rerun the failing job, the CI tests are a bit flaky unfortunately.

[johanbrandhorst]

This seems to be failing consistently https://travis-ci.org/improbable-eng/grpc-web/jobs/441938330, though I doubt it's related to this change:

/home/travis/gopath/src/github.com/improbable-eng/grpc-web/test/custom-karma-driver.ts:140
        self.localTunnel.dispose(function () {
                         ^
TypeError: Cannot read property 'dispose' of undefined

[johanbrandhorst]

Given that it passes everywhere else, I think it might just be a test configuration error. I can't force this through myself but have tried alerting others so we can get this in.

[virtuald]

Ping.

[jonnyreeves]

Just had a look into the build failure, I believe the root cause is the failure to bring up Chrome:

Error: [init({"project":"master","build":"travis_803","acceptSslCerts":true,"defaultVideo":true,"browserstack.local":true,"browserstack.tunnel":true,"browserstack.debug":true,"tunnelIdentifier":"tunnel-0.9422959229946926","browserstack.localIdentifier":"tunnel-0.9422959229946926","testSuite":"client","browserName":"chrome","browserVersion":"42","os":"Windows","os_version":"7"})] The environment you requested was unavailable.
Could not start Browser / Emulator

We are seeing the same failure on master so I am also confident this failure is unrelated to the changes.

I'll merge this through, however we should follow up with fixing this particular browser test, or remove it from the matrix

[jonny-improbable]

@virtuald could you please bring this up to speed with master now #262 was merged? Thanks!

[virtuald]

Looks like it passed. 👍

[johanbrandhorst]

LGTM!