This solves a perf issue for views which produce content that is smaller
than the buffer size of HttpResponseStreamWriter. In this case, the writer
ends up synchronously writing to the Response as part of Dispose which
affects perf.
This change makes ViewComponentResult respect an existing Content-Type
setting on the HttpResponse. Code is very similar to the code in
ViewExector, and includes the same quirks.
Abstractions - Core MVC extensibility
Controllers - MVC implementations of .Abstractions and supporting
contracts
Infrastructure - General purpose support APIs. Metadata APIs that don't
fit clearly with a feature or with .Abstraction