Devtools Animations: Add buffer and effect selection to animation timeline

LayoutTests/http/tests/inspector/elements-test.js

 var initialize_ElementTest = function() {
 
 InspectorTest.preloadPanel("elements");
 
 InspectorTest.inlineStyleSection = function()
 {
     return WebInspector.panels.elements.sidebarPanes.styles._sectionBlocks[0].sections[0];
 }
 
 InspectorTest.computedStyleWidget = function()
@@ skipping 987 matching lines @@
 
     function report(error, result)
     {
         InspectorTest.addResult(idValue + JSON.stringify(result, null, 2));
         callback();
     }
 }
 
 InspectorTest.waitForAnimationAdded = function(callback)
 {
-    InspectorTest.addSniffer(WebInspector.AnimationTimeline.prototype, "_addAnimation", callback);
+    InspectorTest.addSniffer(WebInspector.AnimationTimeline.prototype, "_addAnimationGroup", callback);
 }
 
 InspectorTest.dumpAnimationTimeline = function(timeline)
 {
     for (var nodeUI of timeline._nodesMap.values()) {
         for (nodeRow of nodeUI._rows) {
             for (var ui of nodeRow.animations) {
                 InspectorTest.addResult(ui.animation().type());
                 InspectorTest.addResult(ui._nameElement.outerHTML);
                 InspectorTest.addResult(ui._svg.outerHTML);
             }
         }
     }
 }
 
 };