Remove frame disconnection counter updating in removeDetachedChildren()

This method is only called from destructors or document teardown. We
apparenly also skip it when in Oilpan mode. That would seem to indicate
that by the time we get here there should be no subframes left connected.

Lets change the loop into an ASSERT to verify that.

Review URL: https://codereview.chromium.org/303653005

git-svn-id: svn://svn.chromium.org/blink/trunk@175086 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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

@@ -78,10 +78,7 @@ static void collectChildrenAndRemoveFromOldParent(Node& node, NodeVector& nodes,
 #if !ENABLE(OILPAN)
 void ContainerNode::removeDetachedChildren()
 {
-    if (connectedSubframeCount()) {
-        for (Node* child = firstChild(); child; child = child->nextSibling())
-            child->updateAncestorConnectedSubframeCountForRemoval();
-    }
+    ASSERT(!connectedSubframeCount());
     ASSERT(needsAttach());
     removeDetachedChildrenInContainer<Node, ContainerNode>(*this);
 }