[DevTools] Fix popover regression in M58

third_party/WebKit/Source/devtools/front_end/ui/Popover.js

Index: third_party/WebKit/Source/devtools/front_end/ui/Popover.js
diff --git a/third_party/WebKit/Source/devtools/front_end/ui/Popover.js b/third_party/WebKit/Source/devtools/front_end/ui/Popover.js
index 4036111edd0caf378b969a85449b5918d73b48bf..56779bd0fb5e813bb7485b89d0cc652925e10e43 100644
--- a/third_party/WebKit/Source/devtools/front_end/ui/Popover.js
+++ b/third_party/WebKit/Source/devtools/front_end/ui/Popover.js
@@ -36,8 +36,9 @@ UI.Popover = class extends UI.Widget {
    * @param {!UI.PopoverHelper=} popoverHelper
    */
   constructor(popoverHelper) {
-    super(true);
+    super(false);
     this.markAsRoot();
+    this.element.classList.add('popover-element');
     this.registerRequiredCSS('ui/popover.css');
     this._containerElement = createElementWithClass('div', 'fill popover-container');
     this._popupArrowElement = this.contentElement.createChild('div', 'arrow');