[css-transitions-2] Draft a changes section.

Author: dbaron

css-transitions-2/Overview.bs

@@ -626,6 +626,55 @@ elem.getAnimations()[0].transitionProperty // 'opacity'
 
 </div>
 
+<h2 id="changes">Changes</h2>
+
+<h3 id="changes-fpwd">Changes since Level 1, in First Public Working Draft</h3>
+
+<ul>
+  <li>Transitions can now occur on discretely-animatable properties.  The
+  newly-introduced 'transition-behavior' property allows opting in to this behavior.</li>
+
+  <li>The ''@starting-style'' rule
+  (and {{CSSStartingStyleRule}} interface)
+  is introduced to allow
+  transitions on elements whose style changes
+  from not being rendered to being rendered.</li>
+
+  <li>Interactions with the Web Animations API are more clearly specified:
+
+  <ul>
+
+    <li>The {{CSSTransition}} interface is defined.</li>
+
+    <li>The composite order of the generated animations is defined.</li>
+
+    <li>The animation class of the generated animations is defined.</li>
+
+    <li>The cascade level of animation objects that were created from transitions
+    and then reused through the Web Animations API is defined,
+    along with the concept of [=owning element=] needed to define it.</li>
+
+    <li>The rules for event dispatch have been specified to explain what happens
+    when the animations are seeked or reversed using the Web Animations API.</li>
+
+    <li>Interaction of the Web Animations API with
+    the rules for faster reversing of interrupted transitions
+    is specified.</li>
+
+    <li>[[#requirements-on-pending-style-changes]] are specified.</li>
+  </ul>
+
+  <li>The handling of transitions on elements
+  that are no longer being rendered
+  is more clearly defined
+  (the transitions are canceled
+  and removed from the set of completed transitions).</li>
+
+  </li>
+
+
+</ul>
+
 <h2 id="issues-common">Issues commonly raised as issues with previous levels</h2>
 
 	<p>