Implement tracking and optimizations of packed arrays

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 6bb7893746d794b7654e1fb7dfd85aaf8f9fe569..1c29ea13b2b2dd8a17c5c179635f7ab8362f8c55 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -775,7 +775,7 @@ Handle<JSFunction> Factory::NewFunctionWithPrototype(Handle<String> name,
       instance_size != JSObject::kHeaderSize) {
     Handle<Map> initial_map = NewMap(type,
                                      instance_size,
-                                     FAST_SMI_ONLY_ELEMENTS);
+                                     GetInitialFastElementsKind());
     function->set_initial_map(*initial_map);
     initial_map->set_constructor(*function);
   }
@@ -1013,10 +1013,11 @@ void Factory::EnsureCanContainHeapObjectElements(Handle<JSArray> array) {
 
 void Factory::EnsureCanContainElements(Handle<JSArray> array,
                                        Handle<FixedArrayBase> elements,
+                                       uint32_t length,
                                        EnsureElementsMode mode) {
   CALL_HEAP_FUNCTION_VOID(
       isolate(),
-      array->EnsureCanContainElements(*elements, mode));
+      array->EnsureCanContainElements(*elements, length, mode));
 }