Hydrogen array constructor cleanup and improvements

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index 53dca036b9ebb7b10c728e175221cb78ae4e9554..c3d1c3ac5709b9b36029f85d4614ed9c911ff5d9 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -866,6 +866,11 @@ bool Genesis::InitializeGlobal(Handle<GlobalObject> inner_global,
     array_function->shared()->set_length(1);
 
     Handle<Map> initial_map(array_function->initial_map());
+
+    // This assert protects an optimization in
+    // HGraphBuilder::JSArrayBuilder::EmitMapCode()
+    ASSERT(initial_map->elements_kind() == GetInitialFastElementsKind());
+
     Handle<DescriptorArray> array_descriptors(
         factory->NewDescriptorArray(0, 1));
     DescriptorArray::WhitenessWitness witness(*array_descriptors);