Devtools: Fix appearance of PropertiesWidget in ElementPanel

Source/devtools/front_end/elements/PropertiesWidget.js

Index: Source/devtools/front_end/elements/PropertiesWidget.js
diff --git a/Source/devtools/front_end/elements/PropertiesWidget.js b/Source/devtools/front_end/elements/PropertiesWidget.js
index 3a0600bd368be46012f70829050a7dcebf3e0a4f..d38a5e40b9f97458e94ba5df8a65d4feedefa5de 100644
--- a/Source/devtools/front_end/elements/PropertiesWidget.js
+++ b/Source/devtools/front_end/elements/PropertiesWidget.js
@@ -156,6 +156,7 @@ WebInspector.PropertiesWidget.prototype = {
                 var title = prototype.description;
                 title = title.replace(/Prototype$/, "");
                 var section = new WebInspector.ObjectPropertiesSection(prototype, title);
+                section.element.classList.add("properties-widget-section");
                 this.sections.push(section);
                 this.element.appendChild(section.element);
                 if (expanded[this.sections.length - 1])