Implement Shiny Modern L&F for individual controls, most-commonly-used first. In rough order:
This phase overlaps with phase 2.
Once enough controls are done, wire up the Views versions of WebUI-styled Cocoa dialogs, behind a new MacViewsWebUIDialogs feature. The WebUI-styled Cocoa dialogs are:
Once all of these dialogs are converted and tested behind the feature, we can ship to canary and dev channels and watch for any performance or crash rate regressions. Doing all the WebUI-style dialogs at once will avoid having three separate dialog UIs.
This phase also includes implementation of rubber-band overscroll and fling scrolling. This technology exists already in the renderer compositor - it needs to be transplanted to the ui compositor.
Once WebUI dialogs are converted en masse, we can convert other dialogs to Views individually, and ship them without a flag flip or field trial. Cocoa dialogs that are in native Cocoa style will gradually migrate to Views dialogs that are in the Shiny Modern style.
At this point, all dialogs are in Shiny Modern, but the rest of the browser chrome is still Cocoa.
Implement Cocoa L&F for any controls still needed for omnibox and top chrome. TODO(ellyjones): which controls are these? Implement Views versions of the omnibox and top chrome behind a new flag mac-views-browser-chrome. Get UI review of the new versions of the omnibox and top chrome. Make the Views versions the default.
mac_views_browser=1At this point, all user-visible UI is done via Views, and we need to switch the entire browser to a Views-only build:
Check for performance regressions against mac_views_browser=0. Check for stability regressions against mac_views_browser=0. Check for a11y regressions through manual testing. TODO(ellyjones): Figure out how feasible automated a11y regression testing is. Switch mac_views_browser to 1 for Canary. Cross fingers. Watch metrics carefully. If there's no surprising metrics changes or public outcry, keep mac_views_browser=1 for dev, then beta, then stable.
Since much of the Cocoa code is dead and we are no longer building with mac_views_browser=0, remove dead Cocoa UI code.