[DevTools] Throttle node decorations update in UI

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 25853dbed1a8e951a9e22ec033cf3114cc5f6d58..51268fdc6ff9eda688fd0e6c54cf2511a4ca9e1f 100644
--- a/third_party/WebKit/Source/devtools/front_end/elements/ElementsTreeElement.js
+++ b/third_party/WebKit/Source/devtools/front_end/elements/ElementsTreeElement.js
@@ -53,6 +53,7 @@ Elements.ElementsTreeElement = class extends UI.TreeElement {
       this._canAddAttributes = true;
     this._searchQuery = null;
     this._expandedChildrenLimit = Elements.ElementsTreeElement.InitialChildrenLimit;
+    this._decorationsThrottler = new Common.Throttler(100);
   }
 
   /**
@@ -1086,10 +1087,21 @@ Elements.ElementsTreeElement = class extends UI.TreeElement {
     if (this.isClosingTag())
       return;
 
-    var node = this._node;
-    if (node.nodeType() !== Node.ELEMENT_NODE)
+    if (this._node.nodeType() !== Node.ELEMENT_NODE)
       return;
 
+    this._decorationsThrottler.schedule(this._updateDecorationsInternal.bind(this));
+  }
+
+  /**
+   * @return {!Promise}
+   */
+  _updateDecorationsInternal() {
+    if (!this.treeOutline)
+      return Promise.resolve();
+
+    var node = this._node;
+
     if (!this.treeOutline._decoratorExtensions)
       /** @type {!Array.<!Runtime.Extension>} */
       this.treeOutline._decoratorExtensions = runtime.extensions(Components.DOMPresentationUtils.MarkerDecorator);
@@ -1127,7 +1139,7 @@ Elements.ElementsTreeElement = class extends UI.TreeElement {
       (n === node ? decorations : descendantDecorations).push(decoration);
     }
 
-    Promise.all(promises).then(updateDecorationsUI.bind(this));
+    return Promise.all(promises).then(updateDecorationsUI.bind(this));
 
     /**
      * @this {Elements.ElementsTreeElement}