Allows to get current frame content size, including payload and mime headers.
Every frame have a payload that could be separated into the mime headers and the mime content.
You can get current mime header size by using vortex_frame_get_mime_header_size and current payload size by calling to vortex_frame_get_payload_size.
|frame ||The frame where the current content size will be reported.|
- Current content size or 0 if it fails.