[css-values-4] Rephrase requirements into a list for easier reading. #4329

Author: fantasai

css-values-4/Overview.bs

@@ -1861,26 +1861,32 @@ The Large, Small, and Dynamic Viewport Sizes</h5>
 	</dl>
 
 	Whether the expansion/retraction of a particular interface
+	(A)
 	changes the sizes of all of the [=viewport-percentage lengths=]
 	(and the [=initial containing block=])
 	simultaneously
-	or contributes to the differences between
+	or (B)
+	contributes to the differences between
 	the [=large viewport size=] and [=small viewport size=]
 	is largely UA-dependent.
-	However,
-	UAs <em>must</em> categorize as the latter
-	any changes in interface that happen as a result of scrolling
-	or other frequent page interactions that would disturb the user
-	if they resulted in substantial layout changes.
-	UAs <em>should</em> categorize as the former
-	any changes in interface that have a sufficiently steady state
-	that re-laying out the document into the adjusted space
-	would be beneficial to the user.
-	Additionally,
-	UAs may have some dynamically-shown interfaces which intentionally overlay content
-	and do not cause any shifts in layout
-	(and therefore have no effect on any of the [=viewport-percentage lengths=]);
-	typically on-screen keyboards will fit into this category.
+	However:
+
+	* Changes in interface that happen as a result of scrolling
+		or other frequent page interactions that would disturb the user
+		if they resulted in substantial layout changes
+		must be categorized as the former (A).
+
+	* Changes in interface that have a sufficiently steady state
+		that re-laying out the document into the adjusted space
+		would be beneficial to the user
+		must be categorized as the latter (B).
+
+	* Additionally,
+		UAs may have some dynamically-shown interfaces
+		that intentionally overlay content
+		and do not cause any shifts in layout--
+		and therefore have no effect on any of the [=viewport-percentage lengths=].
+		(Typically on-screen keyboards will fit into this category.)
 
 	In all cases, scrollbars are assumed not to exist.
 	<span class='note'>Note however that the [=initial containing block=]'s size