Removes some old eye-dropper related code in browser.js which was not
used anymore since the devtools menu are added dynamically now.
And replaces the code in devtools/client/menus.js to call the gcli
eyedropper command now instead of the old eyedropper tool.
MozReview-Commit-ID: DMn9eiVOnGY
--HG--
extra : rebase_source : 020558ead3c2c0a11ffbef97da31392a52d135d3