Fix prerenders in the delete list not being returned by PrerenderManager::GetAsValue().
Fix prerenders in the delete list not being returned by
PrerenderManager::GetAsValue().

NetInternalsTest.NetInternalsPrerenderView expects to always
see the prerender as active or in the history, once started.

BUG=91799
TEST=NetInternalsTest.NetInternalsPrerenderView (Currently flaky)

Review URL: http://codereview.chromium.org/7550031

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@95721 0039d316-1c4b-4281-b951-d872f2087c98

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