Deque: Add HeapDeque and prevent buggy use of swap and operator=

R=ager@chromium.org, jochen@chromium.org, mikhail.pozdynakov@intel.com
BUG=

Review URL: https://codereview.chromium.org/228403002

git-svn-id: svn://svn.chromium.org/blink/trunk@171121 bbb929c8-8fbe-4397-9dbb-9b2b20218538