Bug 950026 - Bail out when we don't get an expected return value from AudioClient::IsFormatSupported, instead of asserting. r=kinetik, a=lsblakk

This will fall back to our own channel mapping code, instead of trying to use
the platform's.
Bug 924905 - Do a subsumes check inside the stack iterator. r=jandem, a=lsblakk
Bug 955889 - Restore caching in EnsureKeywordsHash. r=mano, a=lsblakk
Bug 944851 - Don't consider AudioNode input when getting AudioParam values on the main thread. r=ehsan, a=lsblakk
Bug 953288 - Limit length of URLs for display. r=lucasr, a=bajaj
Bug 948139 - Use UITelemetry to capture clicks on the 'switch to desktop' appbar item. r=mbrubeck, a=lsblakk
Bug 944291 - Part 1: Add SplayTree::find. r=waldo, a=lsblakk
Bug 944291 - Part 2: Mark parent frames whose child frames' overflow have changed as always needing UpdateOverflow called. r=matspal, a=lsblakk
Bug 947710 - Stop evaling and catch errors in Manifest Editor. r=vporof, a=lsblakk