The NGHTTP2_ERR_PAUSE library error code is introduced to pause
the execution of nghttp2_session_mem_recv() when that error code
is returned from nghttp2_on_frame_recv_callback or
nghttp2_on_data_chunk_recv_callback. If this happens, the parameters
available for both callbacks are retained until the application
calls nghttp2_session_continue(). The application must retain
input bytes which was used to produce the frame.
After successful call of nghttp2_session_continue, the application
can continue to call nghttp2_session_mem_recv() to process
additional data.
Now NGHTTP2_OPT_NO_AUTO_WINDOW_UPDATE is split into 2 options:
NGHTTP2_OPT_NO_AUTO_STREAM_WINDOW_UPDATE and
NGHTTP2_OPT_NO_AUTO_CONNECTION_WINDOW_UPDATE.
This is preparation for the upcoming removal of END_FLOW_CONTROL
flag. For nghttpx, instead of using END_FLOW_CONTROL to disable
connection-level flow control, increase window size by large
enough value, which is friendly way to current chromium
implementation.