Number of bytes to fetch from the specified offset.
The plug-in seeks within a stream by building a linked list of one or more NPByteRange objects, which represents a set of discontiguous byte ranges. The only Plug-in API call that uses the NPByteRange type is NPN_RequestRead, which allows the plug-in to read specified parts of a file without downloading it.
The plug-in is responsible for deleting NPByteRange objects when finished with them. The browser makes a copy if it needs to keep the objects beyond the call to NPN_RequestRead.