https://bugs.webkit.org/show_bug.cgi?id=106283
[Shadow DOM] HTMLContentElement and HTMLShadowElement should be behind SHADOW_DOM

Reviewed by Kentaro Hara.

No new tests. Covered by existing tests.

This change moves <content> and <shadow> behind
ENABLE(SHADOW_DOM). Note that empty stub definitions are remaining
even after this change. They are for minimizing #if/#endif usage
and won't hurt code size.

* WebCore.exp.in:
* html/InputType.cpp:
(WebCore::InputType::destroyShadowSubtree):
* html/shadow/ContentDistributor.cpp:
(WebCore::ContentDistributor::distribute):
* html/shadow/HTMLContentElement.cpp:
(WebCore):
(WebCore::HTMLContentElement::create):
(WebCore::HTMLContentElement::HTMLContentElement):
* html/shadow/HTMLContentElement.h:
(WebCore):
(HTMLContentElement):
* html/shadow/HTMLShadowElement.cpp:
* html/shadow/HTMLShadowElement.h:
(WebCore):
(WebCore::isHTMLShadowElement):
(WebCore::toHTMLShadowElement):
* html/shadow/TextFieldDecorationElement.cpp:
(WebCore::TextFieldDecorationElement::decorate):
* testing/Internals.cpp:
(WebCore::Internals::createContentElement):
(WebCore::Internals::isValidContentSelect):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@139410 268f45cc-cd09-0410-ab3c-d52691b4dbfc