[css-overflow-3] Pick a single behavior long block ellipsis

Closes #3213

Author: frivoal

css-overflow-3/Overview.bs

@@ -878,17 +878,10 @@ Indicating Block-Axis Overflow: the 'block-ellipsis' property</h3>
 	and require a single behavior.
 	Finding how to break the cycles probably should be defined as well.
 
-	If the <a>block overflow ellipsis</a>
-	is too long to fit in the line,
-	its layout is undefined
-	(The UA may, for example, treat the <a>block overflow ellipsis</a> as an unbreakable string,
-	or it may lay out the string across more than one line,
-	replacing content in earlier lines as well).
-	However, if any part of the [=block overflow ellipsis=] overflows,
-	its rendering is affected by the 'text-overflow' property.
-
-	Issue(3213): There is a suggestion to actually define the behavior
-	when the ellipsis is too long to fit the line.
+	The UA must treat the <a>block overflow ellipsis</a> as an unbreakable string,
+	If any part of the [=block overflow ellipsis=] overflows,
+	it is treated as [=scrollable overflow=],
+	and its rendering is affected by the 'text-overflow' property.
 
 	The <a>block overflow ellipsis</a> does not capture events:
 	pointer events are dispatched to whatever is underneath