Fix usage of pseudo style cache

LayoutTests/fast/css-generated-content/pseudo-animation-before-onload.html

Index: LayoutTests/fast/css-generated-content/pseudo-animation-before-onload.html
diff --git a/LayoutTests/fast/css-generated-content/pseudo-animation-before-onload.html b/LayoutTests/fast/css-generated-content/pseudo-animation-before-onload.html
index ea285ab61a834549a221bbd345e966e2010e0e24..687bdb64cbb87e0889d3a13cf91cff62263e151c 100644
--- a/LayoutTests/fast/css-generated-content/pseudo-animation-before-onload.html
+++ b/LayoutTests/fast/css-generated-content/pseudo-animation-before-onload.html
@@ -4,29 +4,17 @@
 
 <style>
 @-webkit-keyframes example {
-  from {
-    width: 50px;
-    height: 50px;
-  }
-  to {
-    width: 10px;
-    height: 10px;
-  }
+  from { width: 50px; height: 50px; }
+  to { width: 10px; height: 10px; }
 }
 
 @keyframes example {
-  from {
-    width: 50px;
-    height: 50px;
-  }
-  to {
-    width: 10px;
-    height: 10px;
-  }
+  from { width: 50px; height: 50px; }
+  to { width: 10px; height: 10px; }
 }
 
-#after:after,
-#before:before {
+.after:after,
+.before:before {
     content: "";
     display: block;
     position: relative;
@@ -38,8 +26,8 @@
     animation: example 2s;
 }
 
-#before,
-#after {
+.before,
+.after {
     display: inline-block;
     border: 1px solid black;
     background: red;
@@ -47,8 +35,12 @@
 
 </style>
 
-<div id="before"></div>
-<div id="after"></div>
+<div class="before"></div>
+<div class="before" id="before"></div>
+<div class="before"></div>
+<div class="after"></div>
+<div class="after" id="after"></div>
+<div class="after"></div>
 
 <script>
 description('Animations on :before and :after pseudo elements should run when applied before onload.');