[web-animations-1] Inline active duration calculation into definition.

#8985 (comment)

Author: fantasai

web-animations-1/Overview.bs

@@ -2617,9 +2617,21 @@ Animation effects {#animation-effects}
   which is a signed offset from the [=start time=] of the [=animation=].
 
   The length of the [=active interval=] is called the <dfn>active duration</dfn>,
-  the calculation of which is defined in [[#calculating-the-active-duration]].
+  and is determined by the [=iteration duration=] and [=iteration count=].
   Its length determines the upper bound of the [=active interval=].
 
+  <blockquote id="calculating-the-active-duration">
+    [=active duration=] =
+       <code><a>iteration duration</a> × <a>iteration count</a></code>
+  </blockquote>
+
+  If either the [=iteration duration=] or [=iteration count=] are zero,
+  the [=active duration=] is zero.
+
+  Note: This clarification is needed
+  since the result of infinity multiplied by zero
+  is undefined according to IEEE 754-2008.
+
   <div class=informative-bg>
 
     The relationship between
@@ -3165,22 +3177,6 @@ Animation effects {#animation-effects}
 
 </div>
 
-#### Calculating the active duration #### {#calculating-the-active-duration}
-
-  The [=active duration=] is calculated as follows:
-
-  <blockquote>
-    [=active duration=] =
-       <code><a>iteration duration</a> × <a>iteration count</a></code>
-  </blockquote>
-
-  If either the [=iteration duration=] or [=iteration count=] are zero,
-  the [=active duration=] is zero.
-
-  Note: This clarification is needed
-  since the result of infinity multiplied by zero
-  is undefined according to IEEE 754-2008.
-
 ### Direction control ### {#direction-control}
 
   [=Animation effects=] can also be configured
@@ -3273,9 +3269,6 @@ Calculating progress {#core-animation-effect-calculations}
     </figcaption>
   </figure>
 
-  The process for calculating the [=active duration=]
-  is normatively defined in [[#calculating-the-active-duration]].
-
   Having established the [=active duration=],
   the process for transforming an [=animation effect=]’s [=local time=]
   into its [=transformed progress=] ([=iteration progress=])