Avoid calling slower Node::firstChild() / Node::lastChild() when possible

Source/core/dom/Range.cpp

Index: Source/core/dom/Range.cpp
diff --git a/Source/core/dom/Range.cpp b/Source/core/dom/Range.cpp
index 9189f403bbb65bda280a75d7fa493fb648135f57..42cdf88f6004e3f495610b6666b9ab3c5ec43cec 100644
--- a/Source/core/dom/Range.cpp
+++ b/Source/core/dom/Range.cpp
@@ -735,7 +735,7 @@ PassRefPtr<Node> Range::processContentsBetweenOffsets(ActionType action, PassRef
                 result = container->cloneNode(false);
         }
 
-        Node* n = container->firstChild();
+        Node* n = toContainerNode(container)->firstChild();

[esprehn, 2014/06/02 19:03:37]

This is not safe, a DOCUMENT_TYPE_NODE is not a ContainerNode.

[Inactive, 2014/06/02 20:36:18]

Good catch, thanks.

[Inactive, 2014/06/02 20:46:25]

I kept this change out for now.

         Vector<RefPtr<Node> > nodes;
         for (unsigned i = startOffset; n && i; i--)
             n = n->nextSibling();
@@ -870,7 +870,7 @@ void Range::insertNode(PassRefPtr<Node> prpNewNode, ExceptionState& exceptionSta
     if (newNodeType == Node::DOCUMENT_FRAGMENT_NODE && !newNode->isShadowRoot()) {
         // check each child node, not the DocumentFragment itself
         numNewChildren = 0;
-        for (Node* c = newNode->firstChild(); c; c = c->nextSibling()) {
+        for (Node* c = toDocumentFragment(newNode)->firstChild(); c; c = c->nextSibling()) {
             if (!checkAgainst->childTypeAllowed(c->nodeType())) {
                 exceptionState.throwDOMException(HierarchyRequestError, "The node to be inserted contains a '" + c->nodeName() + "' node, which may not be inserted here.");
                 return;
@@ -923,11 +923,11 @@ void Range::insertNode(PassRefPtr<Node> prpNewNode, ExceptionState& exceptionSta
         if (collapsed)
             m_end.setToBeforeChild(*newText);
     } else {
-        RefPtr<Node> lastChild = (newNodeType == Node::DOCUMENT_FRAGMENT_NODE) ? newNode->lastChild() : newNode;
+        RefPtr<Node> lastChild = (newNodeType == Node::DOCUMENT_FRAGMENT_NODE) ? toDocumentFragment(newNode)->lastChild() : newNode;
         if (lastChild && lastChild == m_start.childBefore()) {
             // The insertion will do nothing, but we need to extend the range to include
             // the inserted nodes.
-            Node* firstChild = (newNodeType == Node::DOCUMENT_FRAGMENT_NODE) ? newNode->firstChild() : newNode.get();
+            Node* firstChild = (newNodeType == Node::DOCUMENT_FRAGMENT_NODE) ? toDocumentFragment(newNode)->firstChild() : newNode.get();
             ASSERT(firstChild);
             m_start.setToBeforeChild(*firstChild);
             return;