[css-display] Support display: contents pseudo-elements.

third_party/WebKit/Source/core/layout/LayoutObject.cpp

Index: third_party/WebKit/Source/core/layout/LayoutObject.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutObject.cpp b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
index f9660903f4b0737c6183822d5baf5c0f4d9d1f0c..024e8e5b61fe699460dc69e9bf6d9ff93e783566 100644
--- a/third_party/WebKit/Source/core/layout/LayoutObject.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutObject.cpp
@@ -35,6 +35,7 @@
 #include "core/css/resolver/StyleResolver.h"
 #include "core/dom/AXObjectCache.h"
 #include "core/dom/ElementTraversal.h"
+#include "core/dom/PseudoElement.h"
 #include "core/dom/StyleChangeReason.h"
 #include "core/dom/StyleEngine.h"
 #include "core/dom/shadow/ShadowRoot.h"
@@ -1580,6 +1581,11 @@ void LayoutObject::setPseudoStyle(PassRefPtr<ComputedStyle> pseudoStyle) {
   setStyle(std::move(pseudoStyle));
 }
 
+bool LayoutObject::isPseudoElementGeneratedContentFor(
+    const PseudoElement& pseudo) const {
+  return isAnonymous() && m_node.get() == &pseudo;
+}
+
 void LayoutObject::firstLineStyleDidChange(const ComputedStyle& oldStyle,
                                            const ComputedStyle& newStyle) {
   StyleDifference diff = oldStyle.visualInvalidationDiff(newStyle);
@@ -3072,6 +3078,9 @@ ComputedStyle* LayoutObject::cachedFirstLineStyle() const {
 ComputedStyle* LayoutObject::getCachedPseudoStyle(
     PseudoId pseudo,
     const ComputedStyle* parentStyle) const {

[rune, 2017/03/13 10:29:50]

So, longer term, we'd remove this method as well, getting the pseudo style for
::first-line, ::selection, etc from Element as well?

[emilio, 2017/03/13 13:28:31]

Yes, I think that'd be saner.

+  DCHECK_NE(pseudo, PseudoIdBefore);
+  DCHECK_NE(pseudo, PseudoIdAfter);
+
   if (pseudo < FirstInternalPseudoId && !style()->hasPseudoStyle(pseudo))
     return nullptr;