Removed priority based streaming and fast path.

Removed priority based streaming and fast path codes in
preparation for future refactoring. These were polluting core
classes despite having a small user base. In the future, they
may be refactored into the appropriate subclasses and "plugins".

Change-Id: I54562546688c6de468b0068e9b6c65e49c5ec269
Merge topic 'removed-priority-streaming' into master

575ebda2 Removed priority based streaming and fast path.