In HttpStreamAccumulator, our implementation needs to match the one in the Apache core filters impl. Specifically we need to match the impl in core_filters.c ap_core_input_filter. Ideally we should have unit tests to verify that the implementations are consistent.

I believe that this is no longer an issue. Our new input filter has a number of comments explaining when and how it attempts to emulate the behavior of mod_ssl and the core input filter, with references to ssl_engine_io.c and core_filters.c.