Move trace event based implementation parts of TimelineModel into TracingTimelineModel

LayoutTests/inspector/layers/tracing-layer-tree.html

Index: LayoutTests/inspector/layers/tracing-layer-tree.html
diff --git a/LayoutTests/inspector/layers/tracing-layer-tree.html b/LayoutTests/inspector/layers/tracing-layer-tree.html
index 72e78b38bf9ce2bee697d7e65c126d4f1e7999c9..60c94d3f968f85bde7a0b377413d1586d704665c 100644
--- a/LayoutTests/inspector/layers/tracing-layer-tree.html
+++ b/LayoutTests/inspector/layers/tracing-layer-tree.html
@@ -30,13 +30,9 @@ function test()
     var target = /** @type {!WebInspector.Target} */ (WebInspector.targetManager.activeTarget());
     var layerTree = new WebInspector.TracingLayerTree(target);
 
-    var tracineTimelineModel = new WebInspector.TracingTimelineModel(InspectorTest.tracingModel);
-    tracineTimelineModel.willStartRecordingTraceEvents();
-
     function onTracingComplete()
     {
-        tracineTimelineModel.didStopRecordingTraceEvents();
-        var events = tracineTimelineModel.inspectedTargetEvents();
+        var events = InspectorTest.tracingTimelineModel.inspectedTargetEvents();
         for (var i = events.length - 1; i >= 0; --i) {
             if (events[i].phase === WebInspector.TracingModel.Phase.SnapshotObject && events[i].name === "cc::LayerTreeHostImpl") {
                 var rootLayer = events[i].args["snapshot"]["active_tree"]["root_layer"];