Don't snapshot plug-ins that come from the same host as the page
https://bugs.webkit.org/show_bug.cgi?id=117969
<rdar://problem/12885400>

Reviewed by Tim Horton.

If a page is serving plug-in content directly, then that content
is typically very important to the page. For example, embedding
a video or audio player. In this case, don't snapshot the plug-ins.

* html/HTMLPlugInImageElement.cpp:
(WebCore::HTMLPlugInImageElement::subframeLoaderWillCreatePlugIn): Add a test
that compares the plug-in's URL against the main page's URL and don't snapshot
if they are the same.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@151971 268f45cc-cd09-0410-ab3c-d52691b4dbfc