[css-contain] size containment affects intrinsic sizing

Closes #4741

Author: frivoal

css-contain-1/Overview.bs

@@ -178,6 +178,7 @@ Strong Containment: the 'contain' property</h2>
 				contain-size-056.html
 				contain-size-061.html
 				contain-size-062.html
+				contain-size-063.html
 				contain-size-baseline-001.html
 				contain-size-borders.html
 				contain-size-breaks-001.html
@@ -425,6 +426,7 @@ Size Containment</h3>
 	</wpt>
 
 	1. When calculating the size of the [=size-containment/containing box=],
+		including when computing its [=intrinsic size=],
 		it must be treated as having no contents.
 
 		<wpt>
@@ -434,6 +436,7 @@ Size Containment</h3>
 		contain-size-027.html
 		contain-size-061.html
 		contain-size-062.html
+		contain-size-063.html
 		contain-size-borders.html
 		contain-size-fieldset-001.html
 		contain-size-fieldset-002.html

css-contain-2/Overview.bs

@@ -190,6 +190,7 @@ Strong Containment: the 'contain' property</h2>
 				contain-size-056.html
 				contain-size-061.html
 				contain-size-062.html
+				contain-size-063.html
 				contain-size-baseline-001.html
 				contain-size-borders.html
 				contain-size-breaks-001.html
@@ -465,6 +466,7 @@ Size Containment</h3>
 	</wpt>
 
 	1. When calculating the size of the [=size-containment/containing box=],
+		including when computing its [=intrinsic size=],
 		it must be treated as having no contents.
 
 		<wpt>
@@ -474,6 +476,7 @@ Size Containment</h3>
 		contain-size-027.html
 		contain-size-061.html
 		contain-size-062.html
+		contain-size-063.html
 		contain-size-borders.html
 		contain-size-fieldset-001.html
 		contain-size-fieldset-002.html