[DevTools] Cleanup DOMExtension.js.

third_party/WebKit/LayoutTests/http/tests/inspector/layers-test.js

Index: third_party/WebKit/LayoutTests/http/tests/inspector/layers-test.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/inspector/layers-test.js b/third_party/WebKit/LayoutTests/http/tests/inspector/layers-test.js
index 8792490dce3a25ab8fab2c7b94d02eb8c9b8c132..11bdda6e4eb17dfa6dc68ddca8e74627909ea3ab 100644
--- a/third_party/WebKit/LayoutTests/http/tests/inspector/layers-test.js
+++ b/third_party/WebKit/LayoutTests/http/tests/inspector/layers-test.js
@@ -105,13 +105,12 @@ function initialize_LayerTreeTests()
     InspectorTest.dispatchMouseEvent = function(eventType, button, element, offsetX, offsetY)
     {
         var totalOffset = element.totalOffset();
-        var scrollOffset = element.scrollOffset();
         var eventArguments = {
             bubbles: true,
             cancelable: true,
             view: window,
-            screenX: totalOffset.left - scrollOffset.left + offsetX,
-            screenY: totalOffset.top - scrollOffset.top + offsetY,
+            screenX: totalOffset.left - element.scrollLeft + offsetX,
+            screenY: totalOffset.top - element.scrollTop + offsetY,
             clientX: totalOffset.left + offsetX,
             clientY: totalOffset.top + offsetY,
             button: button