Previously we had a special, unshared map on the native context that was
used for results of builtin iterators, which was different from the map
that is created from an object literal like `{value, done}`. This not
only leads to unnecessary polymorphism, but also makes it impossible
for user defined iterators to take the fast-paths that we have in
various places (i.e. in collections or promises).
With this change we now properly share the map for `{value, done}` and
use that for the builtin iterator result objects, as well as the
fast-paths.
Drive-by-fix: Remove the restrictions on map caching and transition
caching during bootstrapping. This no longer makes sense.
Bug: v8:9114, v8:9243
Change-Id: I19eb9071f7ec0ed58f8a6f87eed781bc790174b7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1609794
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61488}
