Don't force-update style and layout in Document::scrollingElement

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index f42226205775d7df98216f125d44c20a63f005cc..57d4c143d1bbbe104682c9d3e117b5083eeb21f1 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -1345,9 +1345,14 @@ Range* Document::caretRangeFromPoint(int x, int y) {
 }
 
 Element* Document::scrollingElement() {
+  if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled() && inQuirksMode())
+    updateStyleAndLayoutTree();
+  return scrollingElementInternal();
+}
+
+Element* Document::scrollingElementInternal() {
   if (RuntimeEnabledFeatures::scrollTopLeftInteropEnabled()) {

[wkorman, 2017/01/11 03:56:39]

Maybe add a DCHECK to ensure we're at LayoutClean?

[chrishtr, 2017/01/11 04:09:09]

Done.

     if (inQuirksMode()) {
-      updateStyleAndLayoutTree();
       HTMLBodyElement* body = firstBodyElement();
       if (body && body->layoutObject() &&
           body->layoutObject()->hasOverflowClip())