Revert "Check and clear date cache in DateCurrentTime, DateLocalTimezone and getTimezoneOffset."

This reverts commit r19711 for breaking WebKit tests.
http://build.chromium.org/p/tryserver.chromium/builders/win_rel/builds/278551/steps/content_browsertests/logs/AccessibilityMessagesQueueWhileSwappedOut

TBR=ulan@chromium.org

Review URL: https://codereview.chromium.org/192903002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@19765 ce2b1a6d-e550-0410-aec6-3dcde31c8c00