[chromium] Remove call to detach WebHelperPluginImpl's frame since it is never attached
https://bugs.webkit.org/show_bug.cgi?id=110668

Patch by David Dorwin <ddorwin@chromium.org> on 2013-02-22
Reviewed by Adam Barth.

This fixes http://crbug.com/172764

* src/WebHelperPluginImpl.cpp:
(WebKit::WebHelperPluginImpl::destoryPage):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143827 268f45cc-cd09-0410-ab3c-d52691b4dbfc