Revert 225588 "Cleanup of QuicInMemoryCache to sync with interna..."
It has introduced a number of memory leaks, see
BUG=299630

> Cleanup of QuicInMemoryCache to sync with internal version.
> 
> Review URL: https://codereview.chromium.org/24596008

TBR=rch@chromium.org

Review URL: https://codereview.chromium.org/25013002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225684 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225684