75bf7638b3 introduced this regression, state must
be assigned as an object, even though one would think it's automagically
initialized to an object. Oh well!

Prepares for the latest eslint & flow-related npm packages which cause
these errors.

Rearrange the ToolbarButtons in the secondary Toolbar in order to mostly
group the media-related ones such as the AudioRouteButton, the
switchCamera button, and the audio-only mode button.

* Javadoc introduced @code as a replacement of <code> and <tt> which is
  better aligned with other javadoc tags such as @link. Use it in the
  Java source code. If we switch to Kotlin, then we'll definitely use
  Markdown.

* There are more uses of @code in the JavaScript source code than <tt>
  so use @code for the sake of consistency. Eventually, I'd rather we
  switch to Markdown because it's easier on my eyes.

* Xcode is plain confused by @code and @link. The Internet says that
  Xcode supports the backquote character to denote the beginning and end
  of a string of characters which should be formatted for display as
  code but it doesn't work for me. <tt> is not rendered at all. So use
  the backquote which is rendered itself. Hopefully, if we switch to
  Markdown, then it'll be common between JavaScript and Objective-C
  source code.

* Implement disabling buttons (like Web had the ability).
* Use consistent colors (e.g. for the buttons) like the rest of the app
  (e.g. WelcomePage).
* Enable AbstractDialog to await a thenable from onSubmit and Dialog to
  render a LoadingIndicator in place of the OK/submit button text.