Release pinned buffers at correct time in WinHttpResponseStream, WinHttpWebSocket

[pgavlin]

This is a potential bug: pinned buffers must not be released until it is guaranteed that no further operations will be made that use those buffers.

[davidsh]

cc: @CIPop @SidharthNabar

[CIPop]

@pgavlin Can you add more details on this please?

[pgavlin]

See e.g. https://github.com/dotnet/corefx/blob/383db8b8a8b5a83e540d7fcb952e0e9b4f2da6c4/src/System.Net.Http.WinHttpHandler/src/System/Net/Http/WinHttpResponseStream.cs

It looks like we may be releasing some pinned buffers early (i.e. before we can be sure that native code will no longer attempt to access them).

[CIPop]

Thanks! (Probably searched for the wrong bug number yesterday.)

https://github.com/dotnet/corefx/search?utf8=✓&q=2508
https://github.com/dotnet/corefx/blob/383db8b8a8b5a83e540d7fcb952e0e9b4f2da6c4/src/System.Net.WebSockets.Client/src/System/Net/WebSockets/WinHttpWebSocket.cs#L721

[SidharthNabar]

Moving to future since this needs non-trivial redesign and may add risk

[davidsh]

We need to fix this in order to fix dotnet/corefx#6142.

[ericeil]

There is still a TODO comment referencing this issue, in WinHttpRequestStream.cs. It does not appear to have been addressed by dotnet/corefx#6500. Reopening this issue.