Simplify the 'Extensions to the DocumentTimeline interface' section

Author: theres-waldo

Overview.bs

@@ -164,6 +164,20 @@ active <strong>and</strong> all the other criteria for the timeline becoming
 active are met. When the trigger becomes inactive, the timeline becomes inactive
 as well.
 
+## Extensions to the {{DocumentTimeline}} interface ## {#document-timeline-interface}
+
+<pre class="idl">
+partial dictionary DocumentTimelineOptions {
+  AnimationTimelineTrigger trigger;
+};
+[Constructor(DocumentTimelineOptions options)]
+partial interface DocumentTimeline {
+  // trigger attribute inherited from AnimationTimeline
+};
+</pre>
+
+Issue: Need to add {{DocumentTimelineOptions}} to [[WEB-ANIMATIONS-1]]
+
 ## Scroll Triggers ## {#scroll-triggers}
 
 ### The {{ScrollDirection}} enumeration ### {#scrolldirection-enumeration}
@@ -308,33 +322,6 @@ 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'>