Reland^3 r22105 "Remove static initializer from isolate"

Reland^3 r22105 "Remove static initializer from isolate"

This time:
When accessing the isolate from the sampler signal handler, don't try
to take the global lock. A sampler should only be active if there is
already an isolate on that thread, so we don't need to check whether
the TLS key is already created.

BUG=none
R=dcarney@chromium.org
LOG=n

Committed: https://code.google.com/p/v8/source/detail?r=22235

[dcarney, 2014-07-07 10:21:49]

lgtm

[jochen (gone - plz use gerrit), 2014-07-07 10:56:44]

Committed patchset #1 manually as r22235 (presubmit successful).