Be more strict about multiple documentElements

Source/core/dom/Document.cpp

Index: Source/core/dom/Document.cpp
diff --git a/Source/core/dom/Document.cpp b/Source/core/dom/Document.cpp
index 63cb1e518c441db49e3ef02308e29485cf4d1bf2..2a39ba3bcdf00131e864e3d56b8e0b20da082772 100644
--- a/Source/core/dom/Document.cpp
+++ b/Source/core/dom/Document.cpp
@@ -3252,9 +3252,9 @@ bool Document::childTypeAllowed(NodeType type) const
     return false;
 }
 
-bool Document::canReplaceChild(const Node& newChild, const Node& oldChild) const
+bool Document::canAcceptChild(const Node& newChild, const Node* oldChild, ExceptionState& exceptionState) const
 {
-    if (oldChild.nodeType() == newChild.nodeType())
+    if (oldChild && oldChild->nodeType() == newChild.nodeType())
         return true;
 
     int numDoctypes = 0;
@@ -3263,7 +3263,7 @@ bool Document::canReplaceChild(const Node& newChild, const Node& oldChild) const
     // First, check how many doctypes and elements we have, not counting
     // the child we're about to remove.
     for (Node& c : NodeTraversal::childrenOf(*this)) {
-        if (c == oldChild)
+        if (oldChild && *oldChild == c)

[esprehn, 2014/12/05 19:18:24]

it might be nice to rename "c" to "child" while you're in here.

             continue;
 
         switch (c.nodeType()) {
@@ -3287,6 +3287,8 @@ bool Document::canReplaceChild(const Node& newChild, const Node& oldChild) const
             case DOCUMENT_FRAGMENT_NODE:
             case DOCUMENT_NODE:
             case TEXT_NODE:
+                exceptionState.throwDOMException(HierarchyRequestError, "Nodes of type '" + newChild.nodeName() +
+                    "' may not be inserted inside nodes of type '#document'.");
                 return false;
             case COMMENT_NODE:
             case PROCESSING_INSTRUCTION_NODE:
@@ -3306,6 +3308,8 @@ bool Document::canReplaceChild(const Node& newChild, const Node& oldChild) const
         case DOCUMENT_FRAGMENT_NODE:
         case DOCUMENT_NODE:
         case TEXT_NODE:
+            exceptionState.throwDOMException(HierarchyRequestError, "Nodes of type '" + newChild.nodeName() +
+                "' may not be inserted inside nodes of type '#document'.");
             return false;
         case COMMENT_NODE:
         case PROCESSING_INSTRUCTION_NODE:
@@ -3319,8 +3323,12 @@ bool Document::canReplaceChild(const Node& newChild, const Node& oldChild) const
         }
     }
 
-    if (numElements > 1 || numDoctypes > 1)
+    if (numElements > 1 || numDoctypes > 1) {
+        exceptionState.throwDOMException(HierarchyRequestError,
+            String::format("Only one %s on document allowed.",
+            numElements > 1 ? "element" : "doctype"));
         return false;
+    }
 
     return true;
 }