[Chromium] Expose WebNode::shadowHost()
https://bugs.webkit.org/show_bug.cgi?id=108681

Reviewed by Dimitri Glazkov.

BrowserPlugin needs to be able to check the event listeners attached to
<webview> and so we expose shadowHost to permit it to poke at the webview
node.

* public/WebNode.h:
* src/WebNode.cpp:
(WebKit::WebNode::shadowHost):
(WebKit):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@141653 268f45cc-cd09-0410-ab3c-d52691b4dbfc