Backed out changeset e4ffa0660d88 (bug 835584) to fix bad commit message.
Backed out f041aad0e8ea (bug 836198) to fix bad commit message.
Bug 836198: Create a "zombie" state for PresShell and use it for the preloaded TabChild PresShell. r=bz a=lsblakk
Bug 835584: Precompile forms.js and preload UserAgentOverrides.jsm. r=fabrice a=lsblakk