DevTools: improve $0 selected element hint in elements

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

Index: third_party/WebKit/Source/devtools/front_end/elements/ElementsTreeElement.js
diff --git a/third_party/WebKit/Source/devtools/front_end/elements/ElementsTreeElement.js b/third_party/WebKit/Source/devtools/front_end/elements/ElementsTreeElement.js
index d5492c6ad3d960b075018923be879930be00870b..79884d53b03d35f25f25329d985a8430f63f8c41 100644
--- a/third_party/WebKit/Source/devtools/front_end/elements/ElementsTreeElement.js
+++ b/third_party/WebKit/Source/devtools/front_end/elements/ElementsTreeElement.js
@@ -236,6 +236,9 @@ Elements.ElementsTreeElement = class extends UI.TreeElement {
       this.selectionElement.className = 'selection fill';
       this.selectionElement.style.setProperty('margin-left', (-this._computeLeftIndent()) + 'px');
       listItemElement.insertBefore(this.selectionElement, listItemElement.firstChild);
+
+      var hintElement = listItemElement.createChild('div', 'selected-hint');

[lushnikov, 2017/03/24 22:05:11]

you gonna re-create this multiple times on .updateTitle()

[luoe, 2017/03/25 01:38:23]

I've added a check to make sure a hintElement doesn't already exist first.

I've also pulled out _createHint() to avoid unnecessary hint making on hover. 
createSelection() in the hovered setter, which we don't want to trigger building
a hint element.

+      hintElement.title = Common.UIString('Use $0 in the console to refer to this element.');
     }
   }