DevTools: move FileSystemMapping under persistence/ module

third_party/WebKit/Source/devtools/front_end/persistence/Persistence.js

Index: third_party/WebKit/Source/devtools/front_end/persistence/Persistence.js
diff --git a/third_party/WebKit/Source/devtools/front_end/persistence/Persistence.js b/third_party/WebKit/Source/devtools/front_end/persistence/Persistence.js
index 9c0d80b8e872393eca11d3883277cc67906856cf..830ae477c41c8bfa3767a2219ff2824236aac4d7 100644
--- a/third_party/WebKit/Source/devtools/front_end/persistence/Persistence.js
+++ b/third_party/WebKit/Source/devtools/front_end/persistence/Persistence.js
@@ -1,6 +1,7 @@
 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+
 /**
  * @unrestricted
  */
@@ -8,7 +9,7 @@ Persistence.Persistence = class extends Common.Object {
   /**
    * @param {!Workspace.Workspace} workspace
    * @param {!Bindings.BreakpointManager} breakpointManager
-   * @param {!Workspace.FileSystemMapping} fileSystemMapping
+   * @param {!Persistence.FileSystemMapping} fileSystemMapping
    */
   constructor(workspace, breakpointManager, fileSystemMapping) {
     super();
@@ -32,7 +33,7 @@ Persistence.Persistence = class extends Common.Object {
   }
 
   /**
-   * @param {function(function(!Persistence.PersistenceBinding), function(!Persistence.PersistenceBinding)):{dispose: function()}} mappingFactory
+   * @param {function(function(!Persistence.PersistenceBinding), function(!Persistence.PersistenceBinding)):!Persistence.MappingSystem} mappingFactory
    */
   _setMappingForTest(mappingFactory) {
     this._mapping.dispose();
@@ -390,5 +391,14 @@ Persistence.PersistenceBinding = class {
   }
 };
 
+/**
+ * @interface
+ */
+Persistence.MappingSystem = function() {};
+
+Persistence.MappingSystem.prototype = {
+  dispose: function() {}
+};
+
 /** @type {!Persistence.Persistence} */
 Persistence.persistence;