Refactoring: The name ContainerNode::removeChildren and ContainerNde::removeAllChilren() is confusing
https://bugs.webkit.org/show_bug.cgi?id=107640

Reviewed by Eric Seidel.

This change renames unsafe removeAllChilren() function to
removeDetachedChildren() and move it to protected visibility.

In theory, the removed nodes should be detached() before. But some
tests violates that assumption. It should be fixed.

No new tests. No behavior change.

* dom/ContainerNode.cpp:
(WebCore::ContainerNode::removeDetachedChildren):
(WebCore::ContainerNode::takeAllChildrenFrom):
(WebCore::ContainerNode::~ContainerNode):
* dom/ContainerNode.h:
(ContainerNode):
* dom/ContainerNodeAlgorithms.h:
(WebCore::removeDetachedChildrenInContainer):
(WebCore):
* dom/Document.cpp:
(WebCore::Document::removedLastRef):
* dom/ShadowRoot.cpp:
(WebCore::ShadowRoot::~ShadowRoot):
* svg/SVGElementInstance.cpp:
(WebCore::SVGElementInstance::detach):
* svg/SVGElementInstance.h:
(SVGElementInstance):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140784 268f45cc-cd09-0410-ab3c-d52691b4dbfc