Timeline: check category presence in list, not string equality

LayoutTests/inspector/tracing-session-id.html

Index: LayoutTests/inspector/tracing-session-id.html
diff --git a/LayoutTests/inspector/tracing-session-id.html b/LayoutTests/inspector/tracing-session-id.html
index cd775f81a98f20bc00b349b13001f33b18028086..3c98f08eff68822cf9127d21f7129d37f7052717 100644
--- a/LayoutTests/inspector/tracing-session-id.html
+++ b/LayoutTests/inspector/tracing-session-id.html
@@ -25,7 +25,7 @@ function test()
             WebInspector.TimelineModel.RecordType.TracingStartedInPage
         ];
 
-        if (event.category !== WebInspector.TracingModel.DevToolsMetadataEventCategory || metadataEvents.indexOf(event.name) < 0)
+        if (!event.hasCategory(WebInspector.TracingModel.DevToolsMetadataEventCategory) || metadataEvents.indexOf(event.name) < 0)
             return;
 
         InspectorTest.assertEquals(InspectorTest.tracingModel().sessionId(), event.args["data"]["sessionId"]);