Are the headers pass to the recipient so far valid? The decoder needs
to process all the headers to maintain state even if there is a
problem. In addition, it is easy for the the intended recipient to
track if the complete set of headers is valid since to do that state
needs to be maintained between the parsing of the initial headers and
the parsing of any trailer headers. The recipient is the best place
to maintain that state.
Inform the recipient of the headers that a stream error needs to be
triggered using the given message when validateHeaders() is
called. This is used when the Parser becomes aware of an error that
is not visible to the recipient.
streamException - The exception to use when resetting the stream