I was considering putting this directly in DefaultHttpDataSource, however:
- We'd need to modify at least OkHttpDataSource as well. I'm not sure whether
Cronet follows this type of redirect automatically or not.
- HttpDataSource instances don't know how they're going to be used, so it's
probably correct that they behave like the underlying network stack.
Issue: #4108
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=192745408
