Ignition requires that objects which will be inserted into the
constant pool are canonicalized (to enable off-thread bytecode
generation). We created a CanonicalizeHandleScope across parse/compile
however this impacts performance (~5-8% on CodeLoad).

Now we localize the CanonicalHandleScope to only the parse /
internalization and renumbering phases where objects are created which
could end up in the constant array pool. This seems to address
the performance regression.

BUG=v8:5203,chromium:634953

Review-Url: https://codereview.chromium.org/2318653002
Cr-Commit-Position: refs/heads/master@{#39443}