Add the comment for why we detach plugin windows when the WebContents is destroyed. This is from the commit log of the patch checking this code in in the old repo.
Add the comment for why we detach plugin windows when the WebContents is
destroyed. This is from the commit log of the patch checking this code in in
the old repo.

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@4314 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser