2ec024e91b
With this change, MessageChannel stores mListener as an IToplevelProtocol rather than a MessageListener (which isn't really a useful concept on its own). The MessageListener methods are split out to IProtocol and IToplevelProtocol. MessageListener gets deleted. Some of the inline functions in MessageChannel had to be moved to MessageChannel.cpp since IToplevelProtocol isn't defined in MessageChannel.h.