Web Animations: Extract an API for servicing animations

LayoutTests/inspector/layer-compositing-reasons.html

Index: LayoutTests/inspector/layer-compositing-reasons.html
diff --git a/LayoutTests/inspector/layer-compositing-reasons.html b/LayoutTests/inspector/layer-compositing-reasons.html
index a5926bdddb4caeee4f11bfcee6707495188d9ed1..ec34d69402c7dafc8f3fa08cd0334e9cfdc5de51 100644
--- a/LayoutTests/inspector/layer-compositing-reasons.html
+++ b/LayoutTests/inspector/layer-compositing-reasons.html
@@ -11,6 +11,12 @@
 <script src="../http/tests/inspector/inspector-test.js"></script>
 <script src="../http/tests/inspector/layers-test.js"></script>
 <script>
+if (window.internals) {
+    document.addEventListener('webkitAnimationStart', function() {
+        internals.pauseAnimations(0);
+    });
+}
+
 function test()
 {
     function dumpCompositingReasons(layer, callback)