[css-overflow-3] Intrinsic block sizes with continue:discard

Measure to the first **forced** break.

Closes #3214

Author: frivoal

css-overflow-3/Overview.bs

@@ -1096,10 +1096,9 @@ Once it is sufficiently stable in this specification,
 			or the position of the first [=unforced break=],
 			which ever comes sooner,
 			is treated as the end of the <a>fragmentation container</a>,
-			and the rest of the <a>fragmented flow</a> is laid out in
-			the next <a>fragmentation container</a> in the <a>fragmentation context</a>.
-			The remaining content after the [=fragmentation break=] is discarded,
+			and the remaining content after the [=fragmentation break=] is discarded,
 			similar to if it were ''display: none'':
+			* It is not rendered
 			* Just as the content is visually hidden, it is not made available for speech rendering
 			* It does not allow user interaction
 			* Issue(2970): Make sure effects on OM are well defined
@@ -1109,17 +1108,20 @@ Once it is sufficiently stable in this specification,
 				Discussions in the <a href="https://lists.w3.org/Archives/Public/www-style/2018Jul/0030.html">Syndey F2F meeting</a>
 				seemed to generally converge on this,
 				but other possibilities were raised.
-			* It is neither rendered,
-				nor measured as part of the box’s contents for the purpose of
-				finding its <a lt="min-content block size">min-content</a>, <a>max-content</a>, or <a lt="automatic size">automatic</a> <a>block sizes</a>
 
-			However, since intrinsic sizes are calculated across all <a>fragmentation containers</a>,
+			However, since intrinsic sizes are calculated across <a>fragmentation containers</a>,
 			this content <em>is</em> taken into account
 			for the purpose of finding the box’s
 			<a lt="min-content inline size">min-content</a> and <a>max-content</a> <a>inline sizes</a>
 			(see [[css-break-3#varying-size-boxes]]).
-
-			Issue(3214): The effect on intrinsic sizing is under discussion.
+			<a lt="min-content inline size">Min-content</a> and <a>max-content</a> <a>block sizes</a>
+			are calculated based on the content
+			from the start of the [=fragmented flow=]
+			to the first [=forced break=] if any,
+			or to the end of the [=fragmented flow=] if there is no forced break.
+
+			Note: Calculating intrinsic block sizes to the first forced <em>or unforced</em> break
+			would cause intrinsic sizes to depend on layout, which would cause circularities.
 
 			The effect on [=multi-column containers=] is to discard any [=overflow column=].