[css-overflow] Block-ellipsis and float clearance

See #14047

TL;DR: don't shift lines down

Author: frivoal

css-overflow-4/Overview.bs

@@ -990,6 +990,18 @@ Indicating Block-Axis Overflow: the 'block-ellipsis' property</h3>
 			line-clamp-auto-041.html
 		</wpt>
 
+		The user agent must not attempt to make room for the ellipsis
+		by other means that displacing content from the end of the line;
+		notably, user agent must not shift down
+		the line box where the ellipsis is to be placed
+		in order to clear a [=float=]
+		or to be positioned in a wider subsequent [=fragmentation container=]
+		even if that would increase the available width.
+
+		<wpt>
+			block-ellipsis-040.html
+		</wpt>
+
 	* The anonymous inline of [=block overflow ellipsis=] is placed
 		after any remaining content,
 		after [[css-text-4#white-space-phase-2]],
@@ -1031,6 +1043,19 @@ Indicating Block-Axis Overflow: the 'block-ellipsis' property</h3>
 			block-ellipsis-034.html
 		</wpt>
 
+	* Normally, if a line box that would have been placed next to a [=float=]
+		is too short to contain any content,
+		it is shifted downward until either some content fits or there are no more floats present.
+		(See [[CSS21#floats]]).
+		However, if, after displacing content to make room for the ellipsis
+		and inserting the ellipsis,
+		the content would be short enough for the line box to fit next to the float,
+		the user agent must not shift the line box down,
+		and must keep it at its original position.
+
+		<wpt>
+			block-ellipsis-041.html
+		</wpt>
 
 	Text <a href="https://www.w3.org/TR/css-text-3/#justification">alignment and justification</a>
 	occurs after placement,