Use Element creation flags on PseudoElement.

It was almost the same. The kNeedsReattachLayoutTree flag was already
set explicitly after creation when needed. The only difference apart
from that was the kChildNeedsStyleRecalcFlag. Having that set on pseudo
elements also should not hurt.

Change-Id: I354beda2cee8c5c0f3c585a79141a74e3675bced
Reviewed-on: https://chromium-review.googlesource.com/c/1311921Reviewed-by: Anders Ruud <andruud@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604560}

third_party/blink/renderer/core/dom/node.h

@@ -948,8 +948,6 @@ class CORE_EXPORT Node : public EventTarget {
     kCreateDocument = kCreateContainer | kIsConnectedFlag,
     kCreateV0InsertionPoint = kCreateHTMLElement | kIsV0InsertionPointFlag,
     kCreateEditingText = kCreateText | kHasNameOrIsEditingTextFlag,
-    kCreatePseudoElement = kDefaultNodeFlags | kIsContainerFlag |
-                           kIsElementFlag | kNeedsReattachLayoutTree,
   };
 
   Node(TreeScope*, ConstructionType);

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

@@ -90,7 +90,7 @@ String PseudoElement::PseudoElementNameForEvents(PseudoId pseudo_id) {
 PseudoElement::PseudoElement(Element* parent, PseudoId pseudo_id)
     : Element(PseudoElementTagName(pseudo_id),
               &parent->GetDocument(),
-              kCreatePseudoElement),
+              kCreateElement),
       pseudo_id_(pseudo_id) {
   DCHECK_NE(pseudo_id, kPseudoIdNone);
   parent->GetTreeScope().AdoptIfNeeded(*this);