Revert "Unify ways to cache named item in HTMLCollections"

This reverts commit d05ac37966f4016e82aa158175e0fee554648a1d.
It seems to break interactive_ui_test. This is a speculative revert.
I'll revert this revert if it doen't fix the issue.

TBR=abarth,esprehn
BUG=265009

Review URL: https://codereview.chromium.org/21758002

git-svn-id: svn://svn.chromium.org/blink/trunk@155417 bbb929c8-8fbe-4397-9dbb-9b2b20218538