DevTools: Use JS symbols instead of strings for eligible events.

third_party/WebKit/LayoutTests/http/tests/inspector/workspace-test.js

 var initialize_WorkspaceTest = function() {
 
 InspectorTest.createWorkspace = function(ignoreEvents)
 {
     if (InspectorTest.testFileSystemWorkspaceBinding)
         InspectorTest.testFileSystemWorkspaceBinding.dispose();
     if (InspectorTest.testNetworkMapping)
         InspectorTest.testNetworkMapping.dispose();
     WebInspector.fileSystemMapping.resetForTesting();
 
@@ skipping 115 matching lines @@
 }
 
 InspectorTest._defaultWorkspaceEventHandler = function(event)
 {
     var uiSourceCode = event.data;
     var networkURL = WebInspector.networkMapping.networkURL(uiSourceCode);
     if (uiSourceCode.project().type() === WebInspector.projectTypes.Debugger && !networkURL)
         return;
     if (uiSourceCode.project().type() === WebInspector.projectTypes.Service)
         return;
-    InspectorTest.addResult("Workspace event: " + event.type + ": " + uiSourceCode.url() + ".");
+    InspectorTest.addResult(`Workspace event: ${event.type.toString()}: ${uiSourceCode.url()}.`);
 }
 
 InspectorTest.uiSourceCodeURL = function(uiSourceCode)
 {
     return uiSourceCode.url().replace(/.*LayoutTests/, "LayoutTests");
 }
 
 InspectorTest.dumpUISourceCode = function(uiSourceCode, callback)
 {
     InspectorTest.addResult("UISourceCode: " + InspectorTest.uiSourceCodeURL(uiSourceCode));
@@ skipping 41 matching lines @@
     function uiSourceCodeAdded(event)
     {
         if (event.data.name() === name) {
             WebInspector.workspace.removeEventListener(WebInspector.Workspace.Events.UISourceCodeAdded, uiSourceCodeAdded);
             setImmediate(callback);
         }
     }
 }
 
 };