This commit changes "op_http_response_write" to first send response chunk
and then poll the underlying HTTP connection.
Previously after writing a chunk of response HTTP connection wasn't polled
and thus data wasn't written to the socket until after next op interacting
with the connection.
Waiting on next request in Deno.serveHttp() API hanged
when responses were using ReadableStream. This was caused
by op_http_request_next op that was never woken after
response was fully written. This commit adds waker field to
DenoService which is called after response is finished.
This commit adds "CancelHandle" to "ConnResource" and changes
"op_http_next_request" to await for the cancel signal. In turn
when async iterating over "Deno.HttpConn" the iterator breaks
upon closing of the resource.
This commit fixes the URL returned from `request.url` in the HTTP server
to be fully qualified. This previously existed, but was removed and
accidentially not readded during optimizations of the HTTP ops.
Returning a non fully qualified URL from `Request#url` is not spec
compliant.
