fix tests (revert partially for #64597)

src/vs/workbench/parts/webview/electron-browser/webviewEditorInput.ts

@@ -12,6 +12,7 @@ import { IPartService, Parts } from 'vs/workbench/services/part/common/partServi
 import * as vscode from 'vscode';
 import { WebviewEvents, WebviewInputOptions, WebviewReviver } from './webviewEditorService';
 import { WebviewElement } from './webviewElement';
+import { TPromise } from 'vs/base/common/winjs.base';
 
 export class WebviewEditorInput extends EditorInput {
 	private static handlePool = 0;
@@ -221,7 +222,7 @@ export class WebviewEditorInput extends EditorInput {
 			return this.reviver.reviveWebview(this).then(() => new EditorModel());
 		}
 
-		return Promise.resolve(new EditorModel());
+		return TPromise.as(new EditorModel());
 	}
 
 	public supportsSplitEditor() {