[runtime] Fix class literal instantiation.

Class' prototype temporarily got properies backing store inconsistent with
the map which obviously confused heap verifier.

Bug: v8:5799
Change-Id: Ie28b0418daa657763d07c8a928851111680718ed
Reviewed-on: https://chromium-review.googlesource.com/777560
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49460}

src/runtime/runtime-classes.cc

@@ -468,8 +468,6 @@ bool InitClassPrototype(Isolate* isolate,
     map->set_migration_target(false);
     map->set_may_have_interesting_symbols(true);
     //  map->set_construction_counter(Map::kNoSlackTracking);
-    prototype->set_raw_properties_or_hash(
-        *isolate->factory()->empty_property_dictionary());
 
     // We care about name property only for class constructor.
     const bool install_name_accessor = false;