Default extension scroll behavior can lead to inaccessible content for keyboard-only users

Describe the bug

In #1269 we found that a guidance page in the extension with no interactive links fails the scrollable-region-focusable rule. Because overflow is not set on insights-root, it is possible for a scrollbar to appear only over the main landmark div excluding the header. When a keyboard-only user tabs to the page, focusing on the body may not be sufficient to scroll the page with the arrow keys. However, if either:

• there are any interactive elements that receive tab focus, or
• the scrollable content is focusable
• the scrollable content is the entire body

scrolling is possible via the keyboard.

We should explore how to structure our default guidance page (and other pages in the extension as well) to ensure they are fully accessible.

To Reproduce Steps to reproduce the behavior:

1. Go to any guidance page, such as the “How to test” pages in the launchpad
2. Remove any interactive links via code or devtools
3. Try to scroll the page with the keyboard only

CodePen repro example

https://codepen.io/karansin/pen/VwZgaxR

Expected behavior

The user should be able to scroll content with the arrow keys only.

Extension (please complete the following information)

• OS: Windows
• Version 2.9.2

[iamrafan]

@ferBonnin There would be no need for scrollbar if the content is not large enough for the view port and this rule would pass.

Even the current failure occurs only when the view port is so small that a scrollbar is needed to view all the content

[ferBonnin]

validated in insider. looks good.