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

Also make the date cache's timestamp more robust.

BUG=357362
R=svenpanne@chromium.org
LOG=y

Review URL: https://codereview.chromium.org/216613003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20323 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Fix deopts causing uninitialized fixed typed arrays.

The deopt will not happen in production code, since we check that
lengths of fixed typed arrays are smis before calling
TypedArrayInitialze, but that makes deopt bot happy.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/212643016

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20324 ce2b1a6d-e550-0410-aec6-3dcde31c8c00