Of course, it was not the current multiprocess WKWebView, which requires more resources, and not the legacy UIWebView directly, more likely some of its internals.
> Web browsing on the iPhone was always on the feature list, so WebKit would be there, and the editing code came along with it. We needed to decide how other styled text would work, like in Notes. Should we bring over the AppKit text system?
> Eventually, we decided not to. We were so pressed for memory that fitting two styled text systems was judged too much, so I used WebKit to back UITextField and UITextView. I’m pretty sure it stayed that way until iOS 7.
That's truly surprising! I stand corrected.
To quote two of the tweets:
> Web browsing on the iPhone was always on the feature list, so WebKit would be there, and the editing code came along with it. We needed to decide how other styled text would work, like in Notes. Should we bring over the AppKit text system?
> Eventually, we decided not to. We were so pressed for memory that fitting two styled text systems was judged too much, so I used WebKit to back UITextField and UITextView. I’m pretty sure it stayed that way until iOS 7.