deps: backport 1f8555 from v8's upstream
Original commit message:
api: introduce SealHandleScope
When debugging Handle leaks in io.js we found it very convenient to be
able to Seal some specific (root in our case) scope to prevent Handle
allocations in it, and easily find leakage.
R=yangguo
BUG=
Review URL: https://codereview.chromium.org/1079713002
Cr-Commit-Position: refs/heads/master@{#27766}
Should help us identify and fix Handle leaks in core and user-space code.
NOTE: Works only in Debug build now, but is still better than nothing.
R=@bnoordhuis