[css-text-3] Hang trailing collapsible other space separators instead of removing them (#4290)

Close #4180

Author: frivoal

css-text-3/Overview.bs

@@ -1600,18 +1600,12 @@ Text Processing</h3>
 
       <li>A sequence at the end of a line
         of <a>collapsible</a> [=spaces=]
-        and/or [=other space separators=] whose 'white-space' value collapses spaces
         is removed.
 
         <wpt>
           white-space/line-edge-white-space-collapse-001.html
           white-space/pre-float-001.html
           white-space/pre-wrap-float-001.html
-          white-space/trailing-ideographic-space-001.html
-          white-space/trailing-ideographic-space-002.html
-          white-space/trailing-other-space-separators-001.html
-          white-space/trailing-other-space-separators-003.html
-          white-space/trailing-other-space-separators-004.html
           white-space/trailing-space-before-br-001.html
         </wpt>
         <wpt pathprefix="/css/CSS2/text/">
@@ -1626,10 +1620,20 @@ Text Processing</h3>
           white-space-processing-047.xht
         </wpt>
       <li>If there remains any sequence of <a>white space</a>,
-        [=other space separators=],
-	and/or [=preserved=] [=tabs=]
+        and/or [=other space separators=],
         at the end of a line:
         <ul>
+          <li>If 'white-space' is set to ''white-space/normal'', ''white-space/nowrap'', or ''white-space/pre-line'',
+            the UA must [=hang=] this sequence (unconditionally).
+
+            <wpt>
+              white-space/trailing-ideographic-space-001.html
+              white-space/trailing-ideographic-space-002.html
+              white-space/trailing-other-space-separators-001.html
+              white-space/trailing-other-space-separators-003.html
+              white-space/trailing-other-space-separators-004.html
+            </wpt>
+
           <li>If 'white-space' is set to ''pre-wrap'',
              the UA must [=conditionally hang=] this sequence.
              It may also visually collapse the character advance widths