adding a test for bug 804935 window.tabs dne error
(cherry picked from commit b0a85503f5620de2413b971f89ebd0548d783e33)
Merge pull request #729 from Mossop/bug831643

Bug 831643: context-menu image missing when using SDK > 1.12(cherry picked from commit 5eabf48bb4d3b4555f3806fd98dca99188f33d99)