DevTools: make StylesSourceMapping in charge of creating and removing UISourceCodes

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

Index: third_party/WebKit/Source/devtools/front_end/workspace/Workspace.js
diff --git a/third_party/WebKit/Source/devtools/front_end/workspace/Workspace.js b/third_party/WebKit/Source/devtools/front_end/workspace/Workspace.js
index 28539df498677f437f49a0e16dd7409dc47f7db6..d0c7e240194c33e6afa7e73b2b0d53dda75c41b1 100644
--- a/third_party/WebKit/Source/devtools/front_end/workspace/Workspace.js
+++ b/third_party/WebKit/Source/devtools/front_end/workspace/Workspace.js
@@ -84,6 +84,11 @@ Workspace.Project.prototype = {
   /**
    * @return {boolean}
    */
+  isEmpty() {},
+
+  /**
+   * @return {boolean}
+   */
   isServiceProject() {},
 
   /**
@@ -246,6 +251,13 @@ Workspace.ProjectStore = class {
   }
 
   /**
+   * @return {boolean}
+   */
+  isEmpty() {
+    return !this._uiSourceCodesList.length;
+  }
+
+  /**
    * @return {!Workspace.Workspace}
    */
   workspace() {