DevTools: move FileSystemMapping under persistence/ module

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

 var initialize_PersistenceTest = function() {
 
 InspectorTest.preloadModule("persistence");
 InspectorTest.preloadModule("sources");
 
 Runtime.experiments.enableForTest("persistenceValidation");
 
 Persistence.PersistenceBinding.prototype.toString = function()
 {
     var lines = [
@@ skipping 31 matching lines @@
     }
 }
 
 InspectorTest.addFooJSFile = function(fs)
 {
     return fs.root.mkdir("inspector").mkdir("persistence").mkdir("resources").addFile("foo.js", "\n\nwindow.foo = ()=>'foo';");
 }
 
 InspectorTest.forceUseDefaultMapping = function() {
     Persistence.persistence._setMappingForTest((bindingCreated, bindingRemoved) => {
-        return new Persistence.DefaultMapping(Workspace.workspace, Workspace.fileSystemMapping, bindingCreated, bindingRemoved);
+        return new Persistence.DefaultMapping(Workspace.workspace, Persistence.fileSystemMapping, bindingCreated, bindingRemoved);
     });
 }
 
 InspectorTest.initializeTestMapping = function() {
     var testMapping;
     Persistence.persistence._setMappingForTest((bindingCreated, bindingRemoved) => {
         testMapping = new TestMapping(bindingCreated, bindingRemoved);
         return testMapping;
     });
     return testMapping;
@@ skipping 40 matching lines @@
     }
 
     dispose() {
         for (var binding of this._bindings)
             this._onBindingRemoved.call(null, binding);
         this._bindings.clear();
     }
 }
 
 }