Move Layout Tree Construction code into Element::rebuildLayoutTree()

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 047e339cba3e817a5c7eb056291cb3d2776f7584..35d54685e34eb107deb829435a20c713570b2858 100644
--- a/third_party/WebKit/Source/core/dom/Element.cpp
+++ b/third_party/WebKit/Source/core/dom/Element.cpp
@@ -1860,6 +1860,7 @@ void Element::recalcStyle(StyleRecalcChange change, Text* nextTextSibling) {
     if (parentComputedStyle())
       change = recalcOwnStyle(change);
     clearNeedsStyleRecalc();
+    clearNeedsReattachLayoutTree();
   }
 
   // If we reattached we don't need to recalc the style of our descendants
@@ -1891,13 +1892,11 @@ void Element::recalcStyle(StyleRecalcChange change, Text* nextTextSibling) {
                         childNeedsStyleRecalc() ? Force : change);
 
     clearChildNeedsStyleRecalc();
+    clearChildNeedsReattachLayoutTree();
   }
 
   if (hasCustomStyleCallbacks())
     didRecalcStyle(change);
-

[nainar, 2016/10/07 05:05:05]

Moved this to rebuildLayoutTree()

-  if (change == Reattach)
-    reattachWhitespaceSiblingsIfNeeded(nextTextSibling);
 }
 
 PassRefPtr<ComputedStyle> Element::propagateInheritedProperties(
@@ -1946,6 +1945,7 @@ StyleRecalcChange Element::recalcOwnStyle(StyleRecalcChange change) {
 
   if (localChange == Reattach) {
     document().addNonAttachedStyle(*this, std::move(newStyle));
+    setNeedsReattachLayoutTree();
     return rebuildLayoutTree();
   }
 
@@ -1992,12 +1992,49 @@ StyleRecalcChange Element::rebuildLayoutTree() {
   AttachContext reattachContext;
   reattachContext.resolvedStyle = document().getNonAttachedStyle(*this);
   bool layoutObjectWillChange = needsAttach() || layoutObject();
-  reattachLayoutTree(reattachContext);
-  if (layoutObjectWillChange || layoutObject())
+
+  if (needsReattachLayoutTree()) {
+    reattachLayoutTree(reattachContext);
+  } else if (childNeedsReattachLayoutTree()) {
+    reattachPseudoElementLayoutTree(PseudoIdBefore);
+
+    for (Node* child = firstChild(); child && child->isElementNode();
+         child = child->nextSibling())
+      toElement(child)->rebuildLayoutTree();
+
+    reattachPseudoElementLayoutTree(PseudoIdAfter);
+    reattachPseudoElementLayoutTree(PseudoIdBackdrop);
+  }
+
+  if (layoutObjectWillChange || layoutObject()) {
+    // This is information passed on to recalcStyle from recalcDescendantStyles

[nainar, 2016/10/07 05:05:05]

Need to decide if this method is preferable or whether we want to store the Text
node from recalcStyle and use that here in rebuildLayoutTree

+    // we can either traverse the parent's tree to get this node or store it
+    // (like WebKit does).
+    // The choice is between increased time and increased memory complexity
+    Text* lastTextNode = nullptr;
+    for (Node* child = parentNode()->lastChild(); child;
+         child = child->previousSibling()) {
+      if (child->isTextNode()) {
+        lastTextNode = toText(child);
+      } else if (child->isElementNode() && toElement(child) == this) {
+        // This check: toElement(child) == this is present so that we don't do
+        // added work for a siblingNode of this element
+        reattachWhitespaceSiblingsIfNeeded(lastTextNode);
+        break;
+      }
+    }
     return Reattach;
+  }
   return ReattachNoLayoutObject;
 }
 
+void Element::reattachPseudoElementLayoutTree(PseudoId pseudoId) {
+  if (PseudoElement* element = pseudoElement(pseudoId)) {
+    if (element->needsReattachLayoutTree())
+      element->rebuildLayoutTree();
+  }
+}
+
 void Element::updateCallbackSelectors(const ComputedStyle* oldStyle,
                                       const ComputedStyle* newStyle) {
   Vector<String> emptyVector;