However, the release notes do not specify what the name of the scoping class should be.
To clarify, you first go to the Design System CSS Customizer where you can customize the Lightning CSS for your org to style it however you'd like. You save that CSS to a file with the name of your choice (eg MyOrgsCustomStyles.css). Whatever name you choose to save your custom CSS file as, will be the scoping name you'll assign to it in the line containing
!URLFOR. That statement allows
MyOrgsCustomStyles to replace the SLDS styles that would otherwise apply to your page:
//replaces the standard styles in:
When you do this, all the lightning SLDS styles names are used without needing to change them, while also allowing your custom styles to be applied. Your custom styles will use the exact SAME SLDS style names as the standard Lightning SLDS style names with NO change to your page code. This is a feature of SASS that Lightning takes advantage of.
As for the SCOPE, if you look the example CSS file you posted in your own answer to your question, any place in the custom CSS where it doesn't vary from the standard CSS is what affect the definition of the SCOPE of the variations from the standard lightning CSS varies.
I suspect that what you're referring to is that when you add
<APEX:SLDS> to a Visualforce page, you're enabling the Lightning SLDS CSS for that page without having to add it to the page as a linked static resource since it's now available in the Visualforce Domain just as the Standard CSS is currently available without having to load it as a resource. You can set the scope to which it's applied by wrapping the mark-up in
There are limitations on it's use. SVG icons aren’t supported on your page if you don’t have showHeader, standardStylesheets, and sidebar set to false. Also, if you are using the Salesforce sidebar, header, or built-in stylesheets, you can’t add attributes to the html tag. That being said, I believe there's a workaround for the latter. In the LDS system, on components and Flexipages I know you can add the following CSS to your markup to allow HTML to pass through and work as expected:
class="slds-text-longform". It might possibly work with Visualforce pages as well.