Fix: The cached templates in [ClassName]GetTemplate were not separated per world.

BUG=
R=haraken@chromium.org

Review URL: https://codereview.chromium.org/19218002

git-svn-id: svn://svn.chromium.org/blink/trunk@154384 bbb929c8-8fbe-4397-9dbb-9b2b20218538