[WIP] Move script injection into frame script for e10s.
[WIP] Pass URL to sandbox
[WIP] GM_rmc
[WIP] Remove aForce from withAllMenuCommandsForWindowId
[WIP] Remove unused/broken GM_BrowserUI observer

Since GM_BrowserUI is a function, the observer service calls it
directly instead of GM_BrowserUI.observe.
[WIP] Remove unnecessary page{hide,show} listeners in GM_BrowserUI
[WIP] GM_openInTab
[WIP] Fix listening for load events.