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 f5972c64070085e883e96563363867652c7fe6a3..3e06dcdb373afdc4abffd8d54f6d85b8aaed690b 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -4409,13 +4409,21 @@ 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()) {

[dcheng, 2016/12/15 21:35:04]

Nit: this is already null-checked at the beginning of the functoin.

[erikchen, 2016/12/16 20:56:12]

Done.

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