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 ef948f518c45cd9cd95a1baff6af7c947baaaac2..65c6b5394ccc36964246cad56606e2bb3e86db5e 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -4459,17 +4459,31 @@ HTMLFrameOwnerElement* Document::localOwner() const {
 
 void Document::willChangeFrameOwnerProperties(int marginWidth,
                                               int marginHeight,
-                                              ScrollbarMode scrollingMode) {
-  if (!body())
+                                              ScrollbarMode scrollingMode,
+                                              bool isDisplayNone) {
+  if (!documentElement())
     return;
 
   DCHECK(frame() && frame()->owner());
   FrameOwner* owner = frame()->owner();
 
+  if (isDisplayNone != owner->isDisplayNone() && documentElement()) {
+    // TODO: There's almost certainly a more appropriate way of forcing a
+    // reattachLayoutTree on the documentElement().
+    documentElement()->setForceReattach();

[esprehn, 2016/12/10 02:20:55]

You don't need this.

+    setNeedsStyleRecalc(NeedsReattachStyleChange,

[esprehn, 2016/12/10 02:20:55]

It's not valid to set a reattach on the document itself. You want to just do
lazyReattach on the documentElement.

+                        StyleChangeReasonForTracing::create(
+                            StyleChangeReason::IFrameDisplayChanged));
+  }
+
+  if (!body())
+    return;
+
   if (marginWidth != owner->marginWidth())
     body()->setIntegralAttribute(marginwidthAttr, marginWidth);
   if (marginHeight != owner->marginHeight())
     body()->setIntegralAttribute(marginheightAttr, marginHeight);
+
   if (scrollingMode != owner->scrollingMode() && view())
     view()->setNeedsLayout();
 }