Move 'Extensions to the DocumentTimeline interface' under 'Triggering animations'

Author: theres-waldo

Overview.bs

@@ -308,6 +308,33 @@ element.
 </div>
 </div>
 
+## Extensions to the {{DocumentTimeline}} interface ## {#document-timeline-interface}
+
+<pre class="idl">
+partial dictionary DocumentTimelineOptions {
+  ScrollTrigger trigger;
+};
+[Constructor(DocumentTimelineOptions options)]
+partial interface DocumentTimeline {
+  readonly attribute ScrollTrigger trigger;
+};
+</pre>
+
+Issue: We should add the DocumentTimelineOptions to the [[WEB-ANIMATIONS-1]].
+
+Issue: Do we need to repeat the attribute here? It is already listed in [[#extensions-to-animationtimeline]].
+
+The {{DocumentTimeline}} is defined in [[WEB-ANIMATIONS-1]].
+
+If we specified the trigger, this DocumentTimeline will perform following behaviors.
+ 1. If the ScrollTriggerKind of specified options is "offset":
+    1. DocumentTimeline will return current document timeline time after exceed specified offset.
+ 1. If the ScrollTriggerKind of specified options is "range":
+    1. DocumentTimeline wil lreturn current document timeline time when scroll offset is within specified range.
+
+ISSUE: Is it necessary to specify the above, or does it fall out naturally from the definitions of 
+       {{ScrollTrigger}}, {{AnimationTimeline/trigger}}, and [[web-animations#inactive-timeline]]?
+
 ## The 'scroll-container-name' property ## {#scroll-container-name}
 
 <pre class='propdef'>
@@ -534,33 +561,6 @@ as follows:
 
 </div>  <!-- link-for-hint="ScrollTrigger" -->
 
-## Extensions to the {{DocumentTimeline}} interface ## {#document-timeline-interface}
-
-<pre class="idl">
-partial dictionary DocumentTimelineOptions {
-  ScrollTrigger trigger;
-};
-[Constructor(DocumentTimelineOptions options)]
-partial interface DocumentTimeline {
-  readonly attribute ScrollTrigger trigger;
-};
-</pre>
-
-Issue: We should add the DocumentTimelineOptions to the [[WEB-ANIMATIONS-1]].
-
-Issue: Do we need to repeat the attribute here? It is already listed in [[#extensions-to-animationtimeline]].
-
-The {{DocumentTimeline}} is defined in [[WEB-ANIMATIONS-1]].
-
-If we specified the trigger, this DocumentTimeline will perform following behaviors.
- 1. If the ScrollTriggerKind of specified options is "offset":
-    1. DocumentTimeline will return current document timeline time after exceed specified offset.
- 1. If the ScrollTriggerKind of specified options is "range":
-    1. DocumentTimeline wil lreturn current document timeline time when scroll offset is within specified range.
-
-ISSUE: Is it necessary to specify the above, or does it fall out naturally from the definitions of 
-       {{ScrollTrigger}}, {{AnimationTimeline/trigger}}, and [[web-animations#inactive-timeline]]?
-
 ## The 'animation-timeline' property ## {#animation-timeline}
 
 <pre class='propdef'>