[web-animations-1] convert timeline state concept back to previous inactive timeline concept

Author: birtles

web-animations-1/Overview.bs

@@ -632,6 +632,13 @@ purpose of synchronization.
 At any given moment, a [=timeline=] has a single current [=time value=] known
 simply as the timeline's <dfn export for=timeline>current time</dfn>.
 
+A <a>timeline</a> may not always be able to return a meaningful <a>time
+value</a>, but only an <a>unresolved</a> time value.
+For example, it may be defined relative to a moment that has yet to occur,
+such as the firing of a document's load event.
+A <a>timeline</a> is considered to be <dfn lt="inactive timeline">inactive</dfn>
+when its <a>time value</a> is <a>unresolved</a>.
+
 A <a>timeline</a> is <dfn export lt="monotonically increasing timeline"
 local-lt="monotonically increasing">monotonically increasing</dfn> if its
 reported [=timeline/current time=] is always greater than or equal
@@ -712,18 +719,6 @@ animation model to change, but these operations in themselves do not create
 a new [=animation frame=], rather they merely update the current <a>animation
 frame</a>.
 
-<h3 oldids="timeline-phases" id="timeline-states">
-Timeline State</h3>
-
-A [=timeline=]’s <dfn export lt="timeline state">state</dfn> may be either
-<dfn export for=timeline lt="timeline active state|active state">active</dfn> or
-<dfn export for=timeline lt="timeline inactive state|inactive state">inactive</dfn>
-
-A [=timeline=] in the [=timeline inactive state|inactive state=] can
-also be called an <dfn export>inactive timeline</dfn>
-
-An [=inactive timeline=] has an [=unresolved=] [=timeline/current time=].
-
 ### Document timelines ### {#document-timelines}
 
 A <dfn export>document timeline</dfn> is a type of <a>timeline</a> that is <a
@@ -736,24 +731,16 @@ This fixed offset is referred to as the document timeline's <dfn>origin time</df
 Issue(2079): There must be a better term than "origin time"&mdash;
              it's too similar to "time origin".
 
-
-The [=timeline state|state=] of a <a>document timeline</a> at a given moment is
-the [=timeline state|state=] corresponding to the <em>first</em> matching
-condition from the following:
-
-<div class="switch">
-
-:   If the associated document is not an [=active document=] or its
-    [=time origin=] has not yet been established
-::  &rarr; [=timeline inactive state|inactive=]
-:   Otherwise,
-::  &rarr; [=timeline active state|active=]
-
-</div>
+Prior to establishing the [=time origin=] for its associated document,
+a [=document timeline=] is [=inactive timeline|inactive=].
 
 After a [=document timeline=] becomes [=inactive timeline|active=], it is
 [=monotonically increasing=].
 
+A [=document timeline=] that is associated with a {{Document}} which is not
+an [=active document=] is also considered to be
+[=inactive timeline|inactive=].
+
 To <a lt="timeline time to origin-relative time">convert a timeline
 time, |timeline time|, to an origin-relative time</a> for a document timeline,
 |timeline|, return the sum of the |timeline time| and |timeline|'s [=origin
@@ -6365,6 +6352,8 @@ The following changes have been made since the <a
   href="https://www.w3.org/TR/2021/WD-web-animations-1-20210518/">18 May
 2021 Working Draft</a>:
 
+-   Removed the timeline phase concept and `AnimationTimeline.phase` member.
+
 -   Changed the procedure to [=play an animation=] to consistently check
     the *auto-rewind flag* regardless of the [=effective playback rate=].
     Previously the flag was not checked when the effective playback rate was