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..5e02a35786251f612018dd4c899e23e505ecbf2b 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);
-
-  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();
   }
 
@@ -1992,9 +1992,31 @@ 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())

[Bugs Nash, 2016/10/14 00:36:47]

I think this would be better as a DCHECK

[nainar, 2016/10/14 03:28:10]

Done.

+    NOTREACHED();
+
+  if (layoutObjectWillChange || layoutObject()) {
+    // nextTextSibling is passed on to recalcStyle from recalcDescendantStyles
+    // we can either traverse the parent's tree to get this node or store it
+    // (like WebKit does).

[Bugs Nash, 2016/10/14 00:36:47]

I wouldn't include what webkit does in a comment - it might change

[nainar, 2016/10/14 03:28:10]

Done.

+    // The choice is between increased time and increased memory complexity
+    Text* nextTextSibling = nullptr;
+    for (Node* sibling = this->nextSibling(); sibling;
+         sibling = sibling->nextSibling()) {
+      if (sibling->isElementNode() && toElement(sibling)->layoutObject()) {

[Bugs Nash, 2016/10/14 00:36:47]

could avoid this branch by adding it to the for loop conditional

[nainar, 2016/10/14 03:28:10]

Done.

+        break;
+      }
+      if (sibling->isTextNode()) {
+        nextTextSibling = toText(sibling);
+        break;
+      }
+    }
+    reattachWhitespaceSiblingsIfNeeded(nextTextSibling);
     return Reattach;
+  }
   return ReattachNoLayoutObject;
 }