[css-grid-1] Fix off-by-one in favor of Firefox's impl. #2261

Author: tabatkins

css-grid-1/Overview.bs

@@ -959,7 +959,7 @@ Limiting Large Grids</h3>
 	Since memory is limited,
 	UAs may clamp the possible size of the <a>implicit grid</a>
 	to be within a UA-defined limit
-	(which should be at least ten thousand tracks on each side of line 1),
+	(which should accommodate lines at in the range [-10000, 10000]),
 	dropping all lines outside that limit.
 	If a grid item is placed outside this limit,
 	its grid area must be <a>clamped</a> to within this limited grid.
@@ -4710,7 +4710,7 @@ Major Changes</h4>
 				<p>Since memory is limited,
 				UAs may clamp the possible size of the <a>grid</a>
 				to be within a UA-defined limit
-				<ins>(which should be at least one million tracks)</ins>,
+				<ins>(which should accommodate lines at in the range [-10000, 10000]),</ins>,
 				dropping all lines outside that limit.
 				If a grid item is placed outside this limit,
 				its grid area must be <a>clamped</a> to within this limited grid.