NPAPI will not send mouse up events when mouse is outside plugin area

NPAPI will not send mouse up events when mouse is outside plugin area
https://bugs.webkit.org/show_bug.cgi?id=77657
<rdar://problem/10160674>

Reviewed by Andreas Kling.

Source/WebCore:

Export EventHandler::setCapturingMouseEventsNode.

* WebCore.exp.in:

Source/WebKit2:

Use EventHandler::setCapturingMouseEventsNode to ensure we get all the mouse events when the mouse is down.

* WebProcess/Plugins/PluginView.cpp:
(WebKit::PluginView::handleEvent):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@106572 268f45cc-cd09-0410-ab3c-d52691b4dbfc