[css-values] Rewrap; whitespace only.

Author: tabatkins

css-values/Overview.bs

@@ -956,13 +956,14 @@ Font-relative lengths: the ''em'', ''ex'', ''ch'', ''ic'', ''rem'', ''lh'', ''rl
 			Equal to the used x-height of the <a href="https://www.w3.org/TR/css3-fonts/#first-available-font">first available font</a> [[!CSS3-FONTS]].
 			The x-height is so called because it is often equal to the height of the lowercase "x".
 			However, an ''ex'' is defined even for fonts that do not contain an "x".
-			The x-height of a font can be found in different ways. Some fonts
-			contain reliable metrics for the x-height. If reliable font metrics
-			are not available, UAs may determine the x-height from the height
-			of a lowercase glyph. One possible heuristic is to look at how far
-			the glyph for the lowercase "o" extends below the baseline, and
-			subtract that value from the top of its bounding box. In the cases
-			where it is impossible or impractical to determine the x-height,
+			The x-height of a font can be found in different ways.
+			Some fonts contain reliable metrics for the x-height.
+			If reliable font metrics are not available,
+			UAs may determine the x-height from the height of a lowercase glyph.
+			One possible heuristic is to look at
+			how far the glyph for the lowercase "o" extends below the baseline,
+			and subtract that value from the top of its bounding box.
+			In the cases where it is impossible or impractical to determine the x-height,
 			a value of 0.5em must be assumed.
 
 		<dt><dfn id="ch" lt="ch">ch unit</dfn>