Windows 7, GTX 970
Broken: 2.77, 2.78, and newest from builder.blender.org
Worked: The same.
Short description of error
When keying slider for change between IK/FK, keys aren't visible in DopeSheet, Action Editor, Graph Editor. Animation is working, but You can't slide key's, because they are invisible.
Exact steps for others to reproduce the error
Add Pitchipoy rig. Generate it. Add key to IK/FK slider in N panel. Select just hand bones and it should appear.