DevTools: Prevent autocompletion for empty input in ClassesPaneWidget

third_party/WebKit/Source/devtools/front_end/elements/ClassesPaneWidget.js

 // Copyright (c) 2015 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
  */
 Elements.ClassesPaneWidget = class extends UI.Widget {
   constructor() {
     super();
     this.element.className = 'styles-element-classes-pane';
@@ skipping 231 matching lines @@
    * @param {string} expression
    * @param {string} prefix
    * @param {boolean=} force
    * @return {!Promise<!UI.SuggestBox.Suggestions>}
    */
   _buildClassNameCompletions(expression, prefix, force) {
     if (!prefix || force)
       this._classNamesPromise = null;
 
     var selectedNode = UI.context.flavor(SDK.DOMNode);
-    if (!selectedNode || (!prefix && !force && !expression))
+    if (!selectedNode || (!prefix && !force && !expression.trim()))
       return Promise.resolve([]);
 
     if (!this._classNamesPromise || this._selectedFrameId !== selectedNode.frameId())
       this._classNamesPromise = this._getClassNames(selectedNode);
 
     return this._classNamesPromise.then(completions => {
       if (prefix[0] === '.')
         completions = completions.map(value => '.' + value);
       return completions.filter(value => value.startsWith(prefix)).map(completion => ({title: completion}));
     });
   }
 };