Updates to urlbar design, please share your feedback

[daleharvey]

We are in the process of landing some updates to the urlbar and enabling them on nightly for testing and happy to hear some feedback. These changes followed on from a lot of the feedback that was generated with our previous urlbar update (codenamed ScotchBonnet) and address some (not all) of the tradeoffs and concerns as well as bring some general improvements. 

The main change being that the search button is shown consistently now, it no longer appears and disappears when the user types. This makes switching engines to perform a search always accessible and makes it easier to see and install new custom search engines from the sites you visit.

The "search mode" UI is also streamlined, switching between different engines is now always one click away, you no longer need to close the current search mode to pick a new one. 

The urlbar is also clearer about what is about to happen, instead of showing your default search engine logo after typing a url, the urlbar icon now tells you if you are about to search or visit a url.

As mentioned users feedback was pivotal in making these changes so it is always useful to hear what works and doesn't work for your particular workflow. Thanks!

(the patch to enable this landed earlier and so this should be enabled by default in tomorrows nightly, otherwise browser.urlbar.unifiedSearchButton.always and browser.urlbar.unifiedSearchButton.historyInSearchMode are the prefs to preview it).