Return DispayNoneIFrameCreatesNoLayoutObject.

Initially shipped in M65 this feature flag can be removed.

BUG=650433

Change-Id: I2088238be14ec263e2bb81dc0cb9730438315cb2
Reviewed-on: https://chromium-review.googlesource.com/c/1323891Reviewed-by: Erik Chen <erikchen@chromium.org>
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606110}

third_party/blink/renderer/core/dom/document.cc

@@ -5296,11 +5296,9 @@ void Document::WillChangeFrameOwnerProperties(int margin_width,
   DCHECK(GetFrame() && GetFrame()->Owner());
   FrameOwner* owner = GetFrame()->Owner();
 
-  if (RuntimeEnabledFeatures::DisplayNoneIFrameCreatesNoLayoutObjectEnabled()) {
-    if (documentElement()) {
-      if (is_display_none != owner->IsDisplayNone())
-        documentElement()->LazyReattachIfAttached();
-    }
+  if (documentElement()) {
+    if (is_display_none != owner->IsDisplayNone())
+      documentElement()->LazyReattachIfAttached();
   }
 
   // body() may become null as a result of modification event listeners, so we

third_party/blink/renderer/core/layout/layout_view.cc

@@ -229,8 +229,6 @@ bool LayoutView::CanHaveChildren() const {
   FrameOwner* owner = GetFrame()->Owner();
   if (!owner)
     return true;
-  if (!RuntimeEnabledFeatures::DisplayNoneIFrameCreatesNoLayoutObjectEnabled())
-    return true;
   // Although it is not spec compliant, many websites intentionally call
   // Window.print() on display:none iframes. https://crbug.com/819327.
   if (GetDocument().Printing())

third_party/blink/renderer/platform/runtime_enabled_features.json5

@@ -391,10 +391,6 @@
     {
       name: "DisplayLocking",
     },
-    {
-      name: "DisplayNoneIFrameCreatesNoLayoutObject",
-      status: "stable",
-    },
     {
       name: "DocumentCookie",
     },