Implement native _List. constructor in the flow-graph builder.

runtime/lib/array.cc

Index: runtime/lib/array.cc
===================================================================
--- runtime/lib/array.cc	(revision 39516)
+++ runtime/lib/array.cc	(working copy)
@@ -13,26 +13,9 @@
 namespace dart {
 
 DEFINE_NATIVE_ENTRY(List_allocate, 2) {
-  const TypeArguments& type_arguments =
-      TypeArguments::CheckedHandle(isolate, arguments->NativeArgAt(0));
-  const Instance& length = Instance::CheckedHandle(
-      isolate, arguments->NativeArgAt(1));
-  if (!length.IsSmi()) {
-    const String& error = String::Handle(String::NewFormatted(
-        "Length must be an integer in the range [0..%" Pd "].",
-        Array::kMaxElements));
-    Exceptions::ThrowArgumentError(error);
-  }
-  intptr_t len = Smi::Cast(length).Value();
-  if (len < 0 || len > Array::kMaxElements) {
-    const String& error = String::Handle(String::NewFormatted(
-        "Length (%" Pd ") must be an integer in the range [0..%" Pd "].",
-        len, Array::kMaxElements));
-    Exceptions::ThrowArgumentError(error);
-  }
-  const Array& new_array = Array::Handle(Array::New(len));
-  new_array.SetTypeArguments(type_arguments);
-  return new_array.raw();
+  // Implemented in FlowGraphBuilder::VisitNativeBody.
+  UNREACHABLE();
+  return Object::null();
 }