pretty cool! as a mostly chrome user, i'd love to see this land in chrome devtools.
We're excited by the code coverage profiler. Would probably help a lot with promises and async stuff.
Not yet sure about the type annotations... give it a whirl in Safari and holler my way if its being awesome.
If only Safari were multi-platform :-(
It supports both platforms, iOS and Mac OS X!
The Type Profiler and Code Coverage Profiler are all part of WebKit, not Safari.
Coverage is obviously great for testing too. Coverage tools in JavaScript are pretty horrific. It'd be awesome if the dev tools protocol allowed collecting coverage information.
Type profiling as they display it may be overkill, however easily seeing what and where code goes polymorphic and the chain that led to it being so is super useful in performance-sensitive areas. Having to dump hydrogen files and load up IRHydra is pretty much the opposite of fun, as nifty as it is ;(