[map] Boxed double fields can no longer deprecate

Avoid emitting deprecation checks for these fields.

Bug: v8:9606
Change-Id: Id3e317a8c36728b3c7b063743ef9d36aa1209176
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1832170
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64059}

src/objects/map-inl.h

@@ -545,7 +545,8 @@ bool Map::CanBeDeprecated() const {
     PropertyDetails details = instance_descriptors().GetDetails(i);
     if (details.representation().IsNone()) return true;
     if (details.representation().IsSmi()) return true;
-    if (details.representation().IsDouble()) return true;
+    if (details.representation().IsDouble() && FLAG_unbox_double_fields)
+      return true;
     if (details.representation().IsHeapObject()) return true;
     if (details.kind() == kData && details.location() == kDescriptor) {
       return true;