Clarify that border radius reduction is performed on the used value

Author: fantasai

css3-background/Overview.html

@@ -2530,8 +2530,8 @@ <h4 id=corner-overlap><span class=secno>4.4.4. </span>Overlapping Curves</h4>
 
   <p>Corner curves must not overlap: When the sum of any two adjacent border
    radii exceeds the size of the border box, UAs must proportionally reduce
-   all border radii until none of them overlap. The algorithm for reducing
-   radii is as follows:
+   the used value of all border radii until none of them overlap. The
+   algorithm for reducing radii is as follows:
 
   <p>Let <var>f</var> =
    min(<var>L<sub>i</sub></var>/<var>S<sub>i</sub></var>), where <var>i</var>
@@ -2551,6 +2551,9 @@ <h4 id=corner-overlap><span class=secno>4.4.4. </span>Overlapping Curves</h4>
    further reduce the used value of the affected border radii (and only the
    affected border radii) as much as necessary, but no more.
 
+  <p>The rendering of the box must be exactly the same as if the reduced
+   border-radius values were those originally specified.
+
   <div class=example>
    <p>For example, the borders A and D of the <a
     href="#reduced-radius">figure below</a> might be the result of

css3-background/Overview.src.html

@@ -1829,9 +1829,9 @@ <h4 id="corner-transitions">Color and Style Transitions</h4>
 <h4 id="corner-overlap">Overlapping Curves</h4>
 
 <p>Corner curves must not overlap: When the sum of any two adjacent border
-radii exceeds the size of the border box, UAs must proportionally reduce all
-border radii until none of them overlap. The algorithm for reducing radii
-is as follows:
+radii exceeds the size of the border box, UAs must proportionally reduce
+the used value of all border radii until none of them overlap. The algorithm
+for reducing radii is as follows:
 
 <p>Let <var>f</var> = min(<var>L<sub>i</sub></var>/<var>S<sub>i</sub></var>),
 where <var>i</var> ∈ {top, right, bottom, left},
@@ -1852,6 +1852,9 @@ <h4 id="corner-overlap">Overlapping Curves</h4>
 may further reduce the used value of the affected border radii (and
 only the affected border radii) as much as necessary, but no more.
 
+<p>The rendering of the box must be exactly the same as if the reduced
+border-radius values were those originally specified.</p>
+
 <div class=example>
 <p>For example, the borders A and D of the <a
 href="#reduced-radius">figure below</a> might be the