[Shadow DOM] InsertionPoint should have isActive() member function.

[Shadow DOM] InsertionPoint should have isActive() member function.
https://bugs.webkit.org/show_bug.cgi?id=82010

Patch by Takashi Sakamoto <tasak@google.com> on 2012-04-16
Reviewed by Hajime Morita.

This patch adds isActive public member function to InsertionPoint and
makes InsertionPoint elements consider whether active or not.
If an InsertionPoint is inactive, the element is not shadow boundary
and is needed to be rendered.
c.f. https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/shadow/index.html#dfn-active-insertion-point

Test: update existing tests, i.e.
LayoutTests/fast/dom/shadow/shadow-contents-fallback-dynamic.html and
LayoutTests/fast/dom/shadow/shadow-contents-fallback.html

* html/shadow/InsertionPoint.cpp:
(WebCore::InsertionPoint::isActive):
A new public method for checking whether an insertion point is active or inactive.
If active, returns true. Otherwise, false.
(WebCore::InsertionPoint::isShadowBoundary):
Make the method consider whether an insertin point is active or inactive.
(WebCore::InsertionPoint::rendererIsNeeded):
Changed to return true If an insertion point is inactive.
(WebCore::InsertionPoint::attach):
Changed to call only HTMLElement::attach If an insertion point is inactive.
(WebCore::InsertionPoint::detach):
Changed to call only HTMLElement::detach If an insertion point is inactive.
* html/shadow/InsertionPoint.h:
(InsertionPoint):
Added isActive public method.
* dom/NodeRenderingContext.cpp:
(WebCore::NodeRenderingContext::NodeRenderingContext):
Changed to take into account an insertion point's activeness when parent is an insertion point.
(WebCore::NodeRenderingContext::firstRendererOf):
(WebCore::NodeRenderingContext::lastRendererOf):
Changed to take into account an insertion point's activeness.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114334 268f45cc-cd09-0410-ab3c-d52691b4dbfc