Pass nextTextSibling to ::before layout rebuild.

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

Index: third_party/WebKit/Source/core/dom/ContainerNode.cpp
diff --git a/third_party/WebKit/Source/core/dom/ContainerNode.cpp b/third_party/WebKit/Source/core/dom/ContainerNode.cpp
index 46aacf5a09266351f9e34286c481c4bf70ec6f1c..fcd326cb49035a75c0c2afc5156172234dbdcb49 100644
--- a/third_party/WebKit/Source/core/dom/ContainerNode.cpp
+++ b/third_party/WebKit/Source/core/dom/ContainerNode.cpp
@@ -1298,7 +1298,7 @@ void ContainerNode::recalcDescendantStyles(StyleRecalcChange change) {
   }
 }
 
-void ContainerNode::rebuildChildrenLayoutTrees() {
+void ContainerNode::rebuildChildrenLayoutTrees(Text*& nextTextSibling) {
   DCHECK(!needsReattachLayoutTree());
 
   // This loop is deliberately backwards because we use insertBefore in the
@@ -1306,21 +1306,20 @@ void ContainerNode::rebuildChildrenLayoutTrees() {
   // point while building the layout tree.  Having us start from the last child
   // and work our way back means in the common case, we'll find the insertion
   // point in O(1) time.  See crbug.com/288225
-  Text* lastTextNode = nullptr;
   for (Node* child = lastChild(); child; child = child->previousSibling()) {
     bool rebuildChild = child->needsReattachLayoutTree() ||
                         child->childNeedsReattachLayoutTree();
     if (child->isTextNode()) {
       Text* textNode = toText(child);
       if (rebuildChild)
-        textNode->rebuildTextLayoutTree(lastTextNode);
-      lastTextNode = textNode;
+        textNode->rebuildTextLayoutTree(nextTextSibling);
+      nextTextSibling = textNode;
     } else if (child->isElementNode()) {
       Element* element = toElement(child);
       if (rebuildChild)
-        element->rebuildLayoutTree(lastTextNode);
+        element->rebuildLayoutTree(nextTextSibling);
       if (element->layoutObject())
-        lastTextNode = nullptr;
+        nextTextSibling = nullptr;
     }
   }
   // This is done in ContainerNode::attachLayoutTree but will never be cleared
@@ -1329,6 +1328,18 @@ void ContainerNode::rebuildChildrenLayoutTrees() {
   clearChildNeedsReattachLayoutTree();
 }
 
+Text* ContainerNode::findNextTextSibling() const {

[esprehn, 2017/03/28 20:56:51]

This needs a better name, it's doing something very specific that's not just
about next text siblings, it's also looking at stuff like what's in and out of
flow.

This is only used for ShadowRoot, put it in ShadowRoot.cpp as a function not a
method?

[rune, 2017/03/29 10:39:47]

PS2 adds a new method on ShadowRoot instead.

+  for (Node* sibling = firstChild(); sibling;

[esprehn, 2017/03/28 20:56:51]

This is confusing, the function says sibling, but the method is looking at kids?

[rune, 2017/03/29 10:39:47]

Acknowledged.

+       sibling = sibling->nextSibling()) {
+    if (sibling->isTextNode())
+      return toText(sibling);
+    LayoutObject* layoutObject = sibling->layoutObject();
+    if (layoutObject && !layoutObject->isFloatingOrOutOfFlowPositioned())

[esprehn, 2017/03/28 20:56:51]

Why is it safe to call this here? Wouldn't the style be out of date?

[rune, 2017/03/29 10:39:47]

This code should be executed during rebuildLayoutTree only, at which point the
distribution and style is all clean, and the shadow subtree does not need layout
tree rebuilding. See PS2 which adds a lot of DCHECKs.

+      return nullptr;
+  }
+  return nullptr;
+}
+
 void ContainerNode::checkForSiblingStyleChanges(SiblingCheckType changeType,
                                                 Element* changedElement,
                                                 Node* nodeBeforeChange,