Bug 890072 - Part 1: Factor out PlayingRefChanged from DelayNodeEngine; r=roc
Bug 890072 - Part 2: Keep the ConvolverNode alive while its reverb buffers are being exhausted; r=roc
Bug 886618. Part 4: Test. r=ehsan
Bug 867460: remove notion of ShaderProgramTypes from gfx/gl. Carry r=bas.  r=bgirard for the changes.