Bug 924286 - Handle non-unit mVolume in BiquadFilterNode. r=ehsan, a=lsblakk
Bug 898291 - Erase azimuth/elevation history when reset()ing HRTFPanner. r=ehsan, a=lsblakk

So that old cross-fade info does not distort new sound when a PannerNode
finishes and restarts.
Bug 898291 - Remove unused PannerNodeEngine model type variables. r=ehsan, a=lsblakk
Bug 898291 - Skip HRTF panner processing when input has been null long enough for output to be null. r=ehsan, a=lsblakk
Bug 921695 - Part 1: Add convert function. r=karlt, a=lsblakk
Bug 921695 - Part 2: Modify callers. r=karlt, a=lsblakk
Bug 933156 - Don't send null input to EqualPowerPanningFunction. r=roc, a=lsblakk