Oilpan: Move USED_FROM_MULTIPLE_THREADS macros to ThreadState.h

- Move the existing macros to ThreadState.h.
- Add the macros for TextDecoder and TextEncoder. Their constructors are exposed to workers, so they can be touched by workers.

Review URL: https://codereview.chromium.org/159843004

git-svn-id: svn://svn.chromium.org/blink/trunk@167004 bbb929c8-8fbe-4397-9dbb-9b2b20218538