DevTools: Improve performance of the element breadcrumbs.

Source/devtools/front_end/treeoutline.js

Index: Source/devtools/front_end/treeoutline.js
diff --git a/Source/devtools/front_end/treeoutline.js b/Source/devtools/front_end/treeoutline.js
index 37f0b0f18b6769062b2c79d0f9065f249cb6c089..bf17bc05bc13c61aa82a5cadd6f50e0c85d7e917 100644
--- a/Source/devtools/front_end/treeoutline.js
+++ b/Source/devtools/front_end/treeoutline.js
@@ -51,9 +51,9 @@ function TreeOutline(listNode, nonFocusable)
     this.setFocusable(!nonFocusable);
     this._childrenListNode.addEventListener("keydown", this._treeKeyDown.bind(this), true);
 
-    /** @type {!Map.<Object, !Array.<!TreeElement>>} */
+    /** @type {!Map.<!Object, !Array.<!TreeElement>>} */
     this._treeElementsMap = new Map();
-    /** @type {!Map.<Object, boolean>} */
+    /** @type {!Map.<!Object, boolean>} */
     this._expandedStateMap = new Map();
 }
 
@@ -265,6 +265,10 @@ TreeOutline.prototype._forgetChildrenRecursive = function(parentElement)
     }
 }
 
+/**
+ * @param {Object} representedObject
+ * @return {TreeElement}
+ */
 TreeOutline.prototype.getCachedTreeElement = function(representedObject)
 {
     if (!representedObject)
@@ -276,6 +280,10 @@ TreeOutline.prototype.getCachedTreeElement = function(representedObject)
     return null;
 }
 
+/**
+ * @param {Object} representedObject
+ * @return {TreeElement}
+ */
 TreeOutline.prototype.findTreeElement = function(representedObject, isAncestor, getParent)
 {
     if (!representedObject)
@@ -306,6 +314,11 @@ TreeOutline.prototype.findTreeElement = function(representedObject, isAncestor,
     return this.getCachedTreeElement(representedObject);
 }
 
+/**
+ * @param {number} x
+ * @param {number} y
+ * @return {TreeElement}
+ */
 TreeOutline.prototype.treeElementFromPoint = function(x, y)
 {
     var node = this._childrenListNode.ownerDocument.elementFromPoint(x, y);