This will be fixed in 126.96.36.199.
The problem is with how we handle height change events from the web view.
When we observe the scroll view's height changed, we get the current intrinsic content size, invalidate it, then get it again (causing a recalculation). Only if the sizes are different do we notify the view controller that the view needs to be resized.
The problem with this approach was that we assumed we were the only ones invalidating the content size. In iOS 10, the intrinsic content size is invalidated when it is first added to the view hierarchy (because the trait environment changes). This makes the flow: get the current intrinsic content size (causing recalculation), invalidate it, then get it again (causing recalculation). In this case, the content size is always the same and we never notify out.
To fix this, I'm simply recording the last notified content size and notifying if the current size is different from the last recorded size.