Revert "Remove IsInitialized checks from inlined API functions."

Revert "Remove IsInitialized checks from inlined API functions."

This reverts r15277 due to failures in layout tests. Apparently Blink
still initializes the Isolate by calling v8::Null() as the first API
function on some paths.

TBR=svenpanne@chromium.org
TEST=webkit:crypto/worker-random-values-concurrent.html

Committed: http://code.google.com/p/v8/source/detail?r=15281

[Michael Starzinger, 2013-06-24 11:10:51]

Committed patchset #1 manually as r15281 (presubmit successful).