DevTools: Create 2D slider for shadow-editor offset

third_party/WebKit/Source/devtools/front_end/platform/DOMExtension.js

Index: third_party/WebKit/Source/devtools/front_end/platform/DOMExtension.js
diff --git a/third_party/WebKit/Source/devtools/front_end/platform/DOMExtension.js b/third_party/WebKit/Source/devtools/front_end/platform/DOMExtension.js
index 37d6097d418e728f8da60aa54f874e6b72519813..d87167dbca7e43776aec091e1e863ece587b7c7f 100644
--- a/third_party/WebKit/Source/devtools/front_end/platform/DOMExtension.js
+++ b/third_party/WebKit/Source/devtools/front_end/platform/DOMExtension.js
@@ -932,6 +932,17 @@ Document.prototype.deepElementFromPoint = function(x, y)
 }
 
 /**
+ * @return {?Element}
+ */
+Document.prototype.deepActiveElement = function()
+{
+    var activeElement = this.activeElement;
+    while (activeElement && activeElement.shadowRoot && activeElement.shadowRoot.activeElement)
+        activeElement = activeElement.shadowRoot.activeElement;
+    return activeElement;
+}
+
+/**
  * @param {!Event} event
  * @return {boolean}
  */