Revert "Unify ways to cache named item in HTMLCollections"

This reverts commit 5705911a4713a1370967ffe9630cb1a9ed6fd2b0.

It makes fast/events/window-onerror-02.html crash.
BUG=265009
TBR=abarth

Review URL: https://codereview.chromium.org/21679004

git-svn-id: svn://svn.chromium.org/blink/trunk@155503 bbb929c8-8fbe-4397-9dbb-9b2b20218538