Support display: contents for elements, first-line and first-letter pseudos.

third_party/WebKit/Source/core/dom/Element.cpp

Index: third_party/WebKit/Source/core/dom/Element.cpp
diff --git a/third_party/WebKit/Source/core/dom/Element.cpp b/third_party/WebKit/Source/core/dom/Element.cpp
index 24b75742fc9986422bbe76bbeb7380fefc21829f..87984872d478602c209f900a75c6850d94ead313 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -1527,7 +1527,8 @@ const AtomicString Element::imageSourceURL() const {
 }
 
 bool Element::layoutObjectIsNeeded(const ComputedStyle& style) {
-  return style.display() != EDisplay::None;
+  return style.display() != EDisplay::None &&
+         style.display() != EDisplay::Contents;
 }
 
 LayoutObject* Element::createLayoutObject(const ComputedStyle& style) {
@@ -1665,9 +1666,20 @@ void Element::attachLayoutTree(const AttachContext& context) {
     data->clearComputedStyle();
   }
 
-  if (!isSlotOrActiveInsertionPoint())
-    LayoutTreeBuilderForElement(*this, context.resolvedStyle)
-        .createLayoutObjectIfNeeded();
+  if (!isSlotOrActiveInsertionPoint()) {
+    LayoutTreeBuilderForElement builder(*this, context.resolvedStyle);
+    builder.createLayoutObjectIfNeeded();
+
+    // Persist the resolved style if we got to the point we needed to compute
+    // the style, and it was a display: contents style, since we need it for our
+    // children.
+    if (ComputedStyle* style = builder.resolvedStyle()) {
+      if (style->display() == EDisplay::Contents) {
+        DCHECK(!layoutObject());
+        storeDisplayContentsStyle(*style);
+      }
+    }
+  }
 
   addCallbackSelectors();
 
@@ -2003,7 +2015,7 @@ StyleRecalcChange Element::rebuildLayoutTree() {
   // sub-trees. At this point no child should need reattaching.
   DCHECK(!childNeedsReattachLayoutTree());
 
-  if (layoutObjectWillChange || layoutObject()) {
+  if (layoutObjectWillChange || layoutObject() || displayContentsStyle()) {
     // nextTextSibling is passed on to recalcStyle from recalcDescendantStyles
     // we can either traverse the current subtree from this node onwards
     // or store it.
@@ -3133,6 +3145,22 @@ const ComputedStyle* Element::ensureComputedStyle(
   return elementStyle->addCachedPseudoStyle(result.release());
 }
 
+const ComputedStyle* Element::displayContentsStyle() const {
+  if (layoutObject() || !hasRareData())
+    return nullptr;
+
+  ComputedStyle* style = elementRareData()->computedStyle();
+  if (!style || style->display() != EDisplay::Contents)
+    return nullptr;
+
+  return style;
+}
+
+void Element::storeDisplayContentsStyle(ComputedStyle& style) {
+  DCHECK_EQ(style.display(), EDisplay::Contents);
+  ensureElementRareData().setComputedStyle(&style);
+}
+
 AtomicString Element::computeInheritedLanguage() const {
   const Node* n = this;
   AtomicString value;