SDK / exoplayer

We need to make sure the original header is retained when we redirect.

I filed a request on Cronet to allow headers to be provided to the UrlRequest#followRedirect method:
https://bugs.chromium.org/p/chromium/issues/detail?id=779611

Until that API is changed, i.e., pulled into GMSCore, and most clients are using the version of GMSCore with the API change, we can stick with this approach.

FYI

Cronet generally uses the original headers on redirect:

http://[]

but modifies the headers for these special cases:

hhttp://[]

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