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

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 e1cbf151fe88f7bbdf108b79356b814a4212a9a5..e32818b8d8cccf937ca61a2b9280ec836068c47c 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -1574,8 +1574,13 @@ const AtomicString Element::imageSourceURL() const {
 }
 
 bool Element::layoutObjectIsNeeded(const ComputedStyle& style) {
-  return style.display() != EDisplay::None &&
-         style.display() != EDisplay::Contents;
+  if (style.display() == EDisplay::None)
+    return false;
+
+  if (style.display() == EDisplay::Contents)
+    return isPseudoElement();

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

What layout object is needed and created for the ::before element in "::before {
display:contents; content: "PASS"}"?

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

Whoops, this is leftover from the previous approach. It'll arrive to
LayoutObject::createObject and return null there (no LayoutObject needed). This
part can be reverted completely.

+
+  return true;
 }
 
 LayoutObject* Element::createLayoutObject(const ComputedStyle& style) {
@@ -2004,9 +2009,13 @@ StyleRecalcChange Element::recalcOwnStyle(StyleRecalcChange change,
       // https://codereview.chromium.org/30453002/
       layoutObject->setStyleInternal(newStyle.get());
     }
-  } else if (localChange != NoChange &&
-             shouldStoreNonLayoutObjectComputedStyle(*newStyle)) {
-    storeNonLayoutObjectComputedStyle(newStyle);
+  } else {
+    if (localChange != NoChange) {
+      if (shouldStoreNonLayoutObjectComputedStyle(*newStyle))
+        storeNonLayoutObjectComputedStyle(newStyle);
+      else if (hasRareData())
+        elementRareData()->clearComputedStyle();
+    }
   }
 
   if (getStyleChangeType() >= SubtreeStyleChange)
@@ -3181,18 +3190,24 @@ const ComputedStyle* Element::ensureComputedStyle(
   if (!pseudoElementSpecifier)
     return elementStyle;
 
-  if (ComputedStyle* pseudoElementStyle =
+  if (ComputedStyle* cached =
           elementStyle->getCachedPseudoStyle(pseudoElementSpecifier))
-    return pseudoElementStyle;
+    return cached;

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

This and the code below duplicates the code in Element::pseudoStyle(). Couldn't
you call pseudoStyle() here instead?

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

No, I can't. We use pseudoStyleForElement instead of getUncachedPseudoStyle,
which makes a difference when calling getComputedStyle(foo, ":internal-pseudo").

+
+  const ComputedStyle* layoutParentStyle = elementStyle;
+  if (hasDisplayContentsStyle()) {
+    LayoutObject* parentLayoutObject =
+        LayoutTreeBuilderTraversal::parentLayoutObject(*this);
+    if (parentLayoutObject)
+      layoutParentStyle = parentLayoutObject->style();
+  }
 
-  // TODO(ecobos): Passing two times elementStyle may be wrong, though we don't
-  // support display: contents elements' pseudo-elements yet, so this is not a
-  // problem for now.
   RefPtr<ComputedStyle> result =
       document().ensureStyleResolver().pseudoStyleForElement(
-          this, PseudoStyleRequest(pseudoElementSpecifier,
-                                   PseudoStyleRequest::ForComputedStyle),
-          elementStyle, elementStyle);
+          this,
+          PseudoStyleRequest(pseudoElementSpecifier,
+                             PseudoStyleRequest::ForComputedStyle),
+          elementStyle, layoutParentStyle);
   DCHECK(result);
   return elementStyle->addCachedPseudoStyle(result.release());
 }
@@ -3276,7 +3291,7 @@ void Element::updatePseudoElement(PseudoId pseudoId, StyleRecalcChange change) {
     // Need to clear the cached style if the PseudoElement wants a recalc so it
     // computes a new style.
     if (element->needsStyleRecalc())
-      layoutObject()->mutableStyle()->removeCachedPseudoStyle(pseudoId);
+      mutableComputedStyle()->removeCachedPseudoStyle(pseudoId);
 
     // PseudoElement styles hang off their parent element's style so if we
     // needed a style recalc we should Force one on the pseudo.  FIXME: We
@@ -3288,9 +3303,8 @@ void Element::updatePseudoElement(PseudoId pseudoId, StyleRecalcChange change) {
     // continuously create and destroy PseudoElements when
     // LayoutObject::isChildAllowed on our parent returns false for the
     // PseudoElement's layoutObject for each style recalc.
-    if (!layoutObject() ||
-        !pseudoElementLayoutObjectIsNeeded(
-            layoutObject()->getCachedPseudoStyle(pseudoId)))
+    if (!canHaveGeneratedPseudo(pseudoId) ||
+        !pseudoElementLayoutObjectIsNeeded(pseudoStyle(pseudoId)))
       elementRareData()->setPseudoElement(pseudoId, nullptr);
   } else if (pseudoId == PseudoIdFirstLetter && element &&
              change >= UpdatePseudoElements &&
@@ -3327,6 +3341,48 @@ bool Element::updateFirstLetter(Element* element) {
   return false;
 }
 
+ComputedStyle* Element::pseudoStyle(PseudoId pseudoId) const {
+  ComputedStyle* style = mutableComputedStyle();
+  DCHECK(pseudoId < FirstInternalPseudoId);
+  if (!style->hasPseudoStyle(pseudoId))
+    return nullptr;
+
+  if (ComputedStyle* cached = style->getCachedPseudoStyle(pseudoId))
+    return cached;
+  RefPtr<ComputedStyle> uncached = getUncachedPseudoStyle(pseudoId);
+  if (uncached)
+    return style->addCachedPseudoStyle(uncached.release());
+  return nullptr;
+}
+
+PassRefPtr<ComputedStyle> Element::getUncachedPseudoStyle(
+    PseudoId pseudoId) const {
+  if (pseudoId == PseudoIdBefore || pseudoId == PseudoIdAfter) {
+    LayoutObject* parentLayoutObject = layoutObject();
+    if (!parentLayoutObject && hasDisplayContentsStyle()) {
+      parentLayoutObject =
+          LayoutTreeBuilderTraversal::parentLayoutObject(*this);
+    }
+    if (!parentLayoutObject)
+      return nullptr;
+    return document().ensureStyleResolver().pseudoStyleForElement(
+        const_cast<Element*>(this), PseudoStyleRequest(pseudoId),
+        computedStyle(), parentLayoutObject->style());
+  }
+  if (!layoutObject())
+    return nullptr;
+  return layoutObject()->getUncachedPseudoStyle(PseudoStyleRequest(pseudoId));
+}
+
+// For display: contents elements, we still need to generate ::before and
+// ::after, but the rest of the pseudo-elements should only be used for elements
+// with an actual layout object.
+bool Element::canHaveGeneratedPseudo(PseudoId pseudoId) const {
+  if (hasDisplayContentsStyle())
+    return pseudoId == PseudoIdBefore || pseudoId == PseudoIdAfter;
+  return !!layoutObject();
+}
+
 void Element::createPseudoElementIfNeeded(PseudoId pseudoId) {
   if (isPseudoElement())
     return;