Don't create layout objects for children of display-none iframes.

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 987f43e2c966951bc6e1f3cf4a3d0644d1e95c0b..f1890c6eb18f8c31a9c4399aed95a6a9e6a0a86d 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -4494,13 +4494,20 @@ HTMLFrameOwnerElement* Document::localOwner() const {
 
 void Document::willChangeFrameOwnerProperties(int marginWidth,
                                               int marginHeight,
-                                              ScrollbarMode scrollingMode) {
-  if (!body())
-    return;
-
+                                              ScrollbarMode scrollingMode,
+                                              bool isDisplayNone) {
   DCHECK(frame() && frame()->owner());
   FrameOwner* owner = frame()->owner();
 
+  if (documentElement()) {
+    if (isDisplayNone != owner->isDisplayNone()) {

[dcheng, 2017/02/05 09:56:08]

Nit: combine with the previous if ()

+      documentElement()->lazyReattachIfAttached();
+    }
+  }
+
+  if (!body())
+    return;
+
   if (marginWidth != owner->marginWidth())
     body()->setIntegralAttribute(marginwidthAttr, marginWidth);
   if (marginHeight != owner->marginHeight())