[contexts] Place the initial JSArray maps on the native context directly.

src/isolate.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/isolate.h"
 
 #include <stdlib.h>
 
 #include <fstream>  // NOLINT(readability/streams)
 #include <sstream>
@@ skipping 2367 matching lines @@
 }
 
 
 CodeTracer* Isolate::GetCodeTracer() {
   if (code_tracer() == NULL) set_code_tracer(new CodeTracer(id()));
   return code_tracer();
 }
 
 
 Map* Isolate::get_initial_js_array_map(ElementsKind kind, Strength strength) {
-  Context* native_context = context()->native_context();
-  Object* maybe_map_array = is_strong(strength)
-                                ? native_context->js_array_strong_maps()
-                                : native_context->js_array_maps();
-  if (!maybe_map_array->IsUndefined()) {
-    Object* maybe_transitioned_map =
-        FixedArray::cast(maybe_map_array)->get(kind);
-    if (!maybe_transitioned_map->IsUndefined()) {
-      return Map::cast(maybe_transitioned_map);
+  if (IsFastElementsKind(kind)) {
+    DisallowHeapAllocation no_gc;
+    Object* const initial_js_array_map = context()->native_context()->get(
+        Context::ArrayMapIndex(kind, strength));
+    if (!initial_js_array_map->IsUndefined()) {
+      return Map::cast(initial_js_array_map);
     }
   }
-  return NULL;
+  return nullptr;
 }
 
 
 bool Isolate::use_crankshaft() const {
   return FLAG_crankshaft &&
          !serializer_enabled_ &&
          CpuFeatures::SupportsCrankshaft();
 }
 
 
@@ skipping 402 matching lines @@
   // Then check whether this scope intercepts.
   if ((flag & intercept_mask_)) {
     intercepted_flags_ |= flag;
     return true;
   }
   return false;
 }
 
 }  // namespace internal
 }  // namespace v8