Revert "Do IDBKey to V8 value conversions lazily."

This reverts commit efe35417c5b8f6a03e92dd71f7ea5d65167abac4.

The new cursor-leak test is flaky on the bots, and work on a follow-up
patch shows that m_request->requestState() calls from key/primaryKey
are not safe.

NOTRY=true
TBR=hclam@chromium.org

Review URL: https://chromiumcodereview.appspot.com/23009012

git-svn-id: svn://svn.chromium.org/blink/trunk@156243 bbb929c8-8fbe-4397-9dbb-9b2b20218538