Keep input accessory view at bottom of screen when keyboard dismissed

[montehurd]

https://phabricator.wikimedia.org/T213450

In this case keyboard dismissal occurs when the editor web view resigns 1st responder.
When this happens the system goes up the responder chain looking for a UIResponder subclass which wants to become 1st responder.

Making SectionEditorViewController able to become 1st responder means it's the first such item in the responder chain encountered when the keyboard is dismissed.

Making its inputAccessoryView return inputViewsController.inputAccessoryView means the accessory view shown will be the one which was previously shown atop the keyboard.

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Looking at how find in page docks its accessory view at bottom when keyboard hidden was helpful:
#794 (comment)
#794 (comment)
#794 (comment)

These were useful too:
https://robots.thoughtbot.com/input-accessorizing-uiviewcontroller
https://developer.apple.com/documentation/uikit/uiresponder/1621119-inputaccessoryview

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Question for @carolynlimadeo - this fix doesn't yet keep Style or TextFormatting header from completely disappearing as seen below. It's pretty easy to fix (just need to move these headers in their own inputAccessoryView's too) but wanted to double-check you wanted that 1st.

[natharateh]

After keyboard is dismissed and toolbar gets docked at the bottom, when I tap on the leftmost icon on the default toolbar ("A"), nothing happens. I have to tap on the webView for the Text formatting input view to appear. And then when I dismiss it by tapping on the "X", the default toolbar won't be there, and if I scroll away the keyboard, no view will be visible at the bottom of the screen.

Repro steps:

1. Scroll to dismiss the keyboard
2. Tap "A" on the default toolbar

Expected:
Text formatting input view appears

Actual:
Nothing happens

Repro steps 2:

1. Scroll to dismiss the keyboard
2. Tap "A" on the default toolbar
3. Tap webView
4. Watch Text formatting input view appear right away
5. Tap X to close

Expected:
Previously visible toolbar appears above the keyboard

Actual:
There's no view above the keyboard

So when you dismiss the keyboard now, there will be no view at the bottom.

[carolynlimadeo]

@montehurd, thanks for pinging me on this.

Would it be possible to show the default toolbar when the keyboard is dismissed instead of the sub-view header? This might involve allowing the subview to scroll off and then triggering the toolbar to appear.

I'm hesitant to keep the sub-view sticky as we're also hoping to have the sub-view be dismissed once it's off the screen.

[montehurd]

@nambatee @joewalsh oops sorry I should have added WIP until I heard back from Carolyn.

[montehurd]

@nambatee good catch - will see if those are still issues after trying Carolyn's suggestion.