MD Settings: fix collapse animation once and for all

chrome/browser/resources/settings/settings_page/settings_section.html

 <link rel="import" href="chrome://resources/html/polymer.html">
-<link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animation-runner-behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/shadow.html">
 <link rel="import" href="/animation/animation.html">
 
 <dom-module id="settings-section">
   <template>
     <style>
       :host {
         display: flex;
         flex-direction: column;
+        /* Margin so the box-shadow isn't clipped during animations. */
+        margin-left: 3px;
+        margin-right: 3px;
         position: relative;
       }
 
       #header {
         margin-bottom: 12px;
       }
 
       #header .title {
         color: var(--paper-grey-600);
         font-size: 13px;
         font-weight: 500;
         margin-top: var(--settings-page-vertical-margin);
       }
 
       #card {
         @apply(--shadow-elevation-2dp);
         background-color: white;
         flex: 1;
         overflow: hidden;
       }
 
+      :host(.expanding) #card,
+      :host(.collapsing) #card,
+      :host(.expanded) #card {
+        @apply(--shadow-elevation-4dp);
+      }
+
+      :host(:not(.expanding):not(.expanded)) #card {
+        /* Keep the fading-out neon-animatable inside the card. */
+        position: relative;
+      }
+
       :host(.expanded) #header {
         display: none;
       }
 
-      :host(.frozen) #card {
-        position: fixed;
-        width: 100%;
-      }
-
-      :host(.expanded.frozen) #card {
-        position: relative;
-      }
-
       :host([hidden-by-search]) {
         display: none;
       }
     </style>
     <div id="header">
       <div class="title">{{pageTitle}}</div>
     </div>
     <div id="card">
       <content id="content"></content>
     </div>
   </template>
   <script src="settings_section.js"></script>
 </dom-module>