Bug 843619: Remove tabs tray menu. [r=mfinkle] [a=bbajaj] [needs-clobber]

--HG--
extra : rebase_source : a22bbb601da7407b10baf933251375f7186409f1
Bug 843619: Remove robocop test for tabs tray menu button. [r=gbrown] [a=bbajaj]

--HG--
extra : rebase_source : ecc7fbf7a7640126ca5e5a397d14c7f2de1eeaf8
Bug 850814: Align the BrowserToolbar's curves properly. [r=mfinkle] [a=bbajaj]

--HG--
extra : rebase_source : 4beda6c2c257f78188cf435770a62d63c4a2707c