Enhance the array access API to deal with any objct that implements the list interface.

vm/object_store.cc

Index: vm/object_store.cc
===================================================================
--- vm/object_store.cc	(revision 849)
+++ vm/object_store.cc	(working copy)
@@ -27,6 +27,7 @@
     four_byte_string_class_(Class::null()),
     bool_interface_(Type::null()),
     bool_class_(Class::null()),
+    list_interface_(Type::null()),
     array_class_(Class::null()),
     immutable_array_class_(Class::null()),
     unhandled_exception_class_(Class::null()),
@@ -133,6 +134,7 @@
     case kIntInterface: return int_interface();
     case kBoolInterface: return bool_interface();
     case kStringInterface: return string_interface();
+    case kListInterface: return list_interface();
     default: break;
   }
   UNREACHABLE();
@@ -162,6 +164,8 @@
     return kBoolInterface;
   } else if (raw_type == string_interface()) {
     return kStringInterface;
+  } else if (raw_type == list_interface()) {
+    return kListInterface;
   }
   return kInvalidIndex;
 }