Merged r20323 into 3.25 branch.

Don't crash if we get a timezone change notification on an uninitialized isolate

BUG=357362
LOG=N
R=danno@chromium.org

Review URL: https://codereview.chromium.org/212123012

git-svn-id: https://v8.googlecode.com/svn/branches/3.25@20403 ce2b1a6d-e550-0410-aec6-3dcde31c8c00