Reflow: add more techniques and examples

[scottaohara]

A follow-on issue to #4055. There were many ideas for additional examples and techniques. But, adding all of those would have extended the time to get the updated understanding doc in front of the working group for discussion.

The following are ideas we should continue to consider / create to further improve the reflow understanding document.

• more examples of expectations of where two-dimensional layout could be used in tandem to other page content which 'should' be able to collapse into a single column.
  • an interface where a sidebar navigation remains persistent, but the remainder of the content should be able to fit within a 320px area.
  • an interface where a chat widget is present in one column, and automated prompts which update in real time to the content of the chat
• examples of UI that has exceptions to Reflow - but where an accessible alternative should still be provided
  • an editable canvas for presentations or website building or a rich text document that needs to be presented as a particular width, but an alternative preview/presentation exists which could then work for reflow.
• examples of where text truncates within form controls (text fields, listbox popups)
• other examples of text with specific formatting requirements (e.g., poetry / potentially other instances of preformatted text)
• examples of how other SCs fail when sticky headers/footers or popups make it difficult to use the underlying page, or re: the popup example, might be positioned off screen.

[mbgower]

I'd add to this list the idea that not all versions of a page need to meet Reflow. If there is another 'view' that provides equivalent function the SC can be met.
Thinking of the variations in MS Word's Comments/Review presentation, one can basically stack the main content and comments views, so that there is no horizontal scrolling required to keep the main and comment in view. I would argue that since the vertically stacked view exists, the SC is met, regardless of whether the side-by-side view passes.