DevTools: make StylesSourceMapping in charge of creating and removing UISourceCodes

third_party/WebKit/Source/devtools/front_end/workspace/Workspace.js

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 66 matching lines @@
   id() {},
 
   /**
    * @return {string}
    */
   type() {},
 
   /**
    * @return {boolean}
    */
+  isEmpty() {},
+
+  /**
+   * @return {boolean}
+   */
   isServiceProject() {},
 
   /**
    * @return {string}
    */
   displayName() {},
 
   /**
    * @param {!Workspace.UISourceCode} uiSourceCode
    * @return {!Promise<?Workspace.UISourceCodeMetadata>}
@@ skipping 142 matching lines @@
   }
 
   /**
    * @return {string}
    */
   displayName() {
     return this._displayName;
   }
 
   /**
+   * @return {boolean}
+   */
+  isEmpty() {
+    return !this._uiSourceCodesList.length;
+  }
+
+  /**
    * @return {!Workspace.Workspace}
    */
   workspace() {
     return this._workspace;
   }
 
   /**
    * @param {string} url
    * @param {!Common.ResourceType} contentType
    * @return {!Workspace.UISourceCode}
@@ skipping 198 matching lines @@
   WorkingCopyCommitted: Symbol('WorkingCopyCommitted'),
   WorkingCopyCommittedByUser: Symbol('WorkingCopyCommittedByUser'),
   ProjectAdded: Symbol('ProjectAdded'),
   ProjectRemoved: Symbol('ProjectRemoved')
 };
 
 /**
  * @type {!Workspace.Workspace}
  */
 Workspace.workspace;