Bug 888528 - Add node deletion/insertion to the walker actor. r=jwalker

--HG--
extra : rebase_source : 8d5b9991371a7dcdceff2cd302e7bc76c8f90ea0
Bug 892100 - Script actor's source loading error reporting broken; r=past
Backed out changeset 817ceeb741b4 (bug 888528) for mochitest-other orange.
Bug 888881 - Use single unicode character … instead of '...' in label profilerStarted; r=robcee
Merge m-c to fx-team.
Bug 867550 - Make browser_aboutHome.js not fail if it starts before but runs past midnight; r=mak
Bug 892766 - SessionStore tests should wait for delayed startup to be finished when opening new windows; r=yoric
Bug 891360 - Move SessionStore I/O logic to a dedicated worker; r=yoric
Bug 891360 - Follow-up to fix syntax error; r=bustage
Bug 890409 - Disable browser_aboutHome.js for intermittent failures; rs=mak
Merge m-c to fx-team.
Fix step-in in chrome debugging by loading the promise library in the debugger server's compartment (Bug 834756); r=dtownsend,vporof
Merge fx-team to m-c.
Merge m-c to birch.