The sloppy block-scoped function declaration placeholder statements
are held in parser_zone_-allocated hashtables. These hashtables are
not updated when local_zone_s are removed. Therefore, the
NewSloppyBlockFunctionStatement method should allocate
SloppyBlockScopeFunctionStatements in the parser_zone_ to avoid a
use-after-free. Scope fixup code may end up updating something which
is thrown away, but this is a small cost and much simpler than
removing dead hashtable entries later.

R=adamk
LOG=Y
BUG=chromium:537816

Review URL: https://codereview.chromium.org/1564923007

Cr-Commit-Position: refs/heads/master@{#33185}