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 fd79b779eabf4799b7ba977e3148225b61db4544..df3c499d00da4d3568c72f7686518dbac2cff4b6 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -1529,7 +1529,8 @@ 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) {
@@ -1667,9 +1668,15 @@ void Element::attachLayoutTree(const AttachContext& context) {
     data->clearComputedStyle();
   }
 
-  if (!isActiveSlotOrActiveInsertionPoint())
-    LayoutTreeBuilderForElement(*this, context.resolvedStyle)
-        .createLayoutObjectIfNeeded();
+  if (!isActiveSlotOrActiveInsertionPoint()) {
+    LayoutTreeBuilderForElement builder(*this, context.resolvedStyle);
+    builder.createLayoutObjectIfNeeded();
+
+    if (ComputedStyle* style = builder.resolvedStyle()) {
+      if (!layoutObject() && shouldStoreNonLayoutObjectComputedStyle(*style))
+        storeNonLayoutObjectComputedStyle(style);
+    }
+  }
 
   addCallbackSelectors();
 
@@ -1968,6 +1975,9 @@ StyleRecalcChange Element::recalcOwnStyle(StyleRecalcChange change,
       // https://codereview.chromium.org/30453002/
       layoutObject->setStyleInternal(newStyle.get());
     }
+  } else if (localChange != NoChange &&
+             shouldStoreNonLayoutObjectComputedStyle(*newStyle)) {
+    storeNonLayoutObjectComputedStyle(newStyle);
   }
 
   if (getStyleChangeType() >= SubtreeStyleChange)
@@ -3120,15 +3130,49 @@ const ComputedStyle* Element::ensureComputedStyle(
           elementStyle->getCachedPseudoStyle(pseudoElementSpecifier))
     return pseudoElementStyle;
 
+  // FIXME(ecobos): Passing two times elementStyle may be wrong, though we don't
+  // support display: contents pseudo-elements yet, so this is not a problem for
+  // now.

[rune, 2016/12/01 15:28:53]

FIXME -> TODO.

It is wrong, but it's not about display:contents on the pseudo element, it's
about display:contents on the pseudo element's parent, right?

That is:

<style>#x { display:contents } #x::before { content: 'X' }</style>
<span>
  <div id="x"></div>
  Y
</span>

[emilio, 2016/12/01 17:32:56]

Right, should've clarified.

   RefPtr<ComputedStyle> result =
       document().ensureStyleResolver().pseudoStyleForElement(
           this, PseudoStyleRequest(pseudoElementSpecifier,
                                    PseudoStyleRequest::ForComputedStyle),
-          elementStyle);
+          elementStyle, elementStyle);
   DCHECK(result);
   return elementStyle->addCachedPseudoStyle(result.release());
 }
 
+const ComputedStyle* Element::nonLayoutObjectComputedStyle() const {
+  if (layoutObject() || !hasRareData())
+    return nullptr;
+
+  return elementRareData()->computedStyle();
+}
+
+bool Element::hasDisplayContentsStyle() const {
+  if (const ComputedStyle* style = nonLayoutObjectComputedStyle())
+    return style->display() == EDisplay::Contents;
+  return false;
+}
+
+bool Element::shouldStoreNonLayoutObjectComputedStyle(
+    const ComputedStyle& style) const {
+#if DCHECK_IS_ON()
+  if (style.display() == EDisplay::Contents)
+    DCHECK(!layoutObject());
+#endif
+
+  return style.display() == EDisplay::Contents ||
+         isHTMLOptGroupElement(*this) || isHTMLOptionElement(*this);
+}
+
+void Element::storeNonLayoutObjectComputedStyle(
+    PassRefPtr<ComputedStyle> style) {
+  DCHECK(style);
+  DCHECK(shouldStoreNonLayoutObjectComputedStyle(*style));
+  ensureElementRareData().setComputedStyle(std::move(style));
+}
+
 AtomicString Element::computeInheritedLanguage() const {
   const Node* n = this;
   AtomicString value;
@@ -3862,6 +3906,7 @@ void Element::inlineStyleChanged() {
                                             StyleChangeReason::Inline));
   DCHECK(elementData());
   elementData()->m_styleAttributeIsDirty = true;
+
   InspectorInstrumentation::didInvalidateStyleAttr(this);
 
   if (MutationObserverInterestGroup* recipients =