Add flag —enable-debugger (default true) in order to disable debugger single stepping code.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 44 matching lines @@
     "When possible, partially or fully overlap the type arguments of a type "
     "with the type arguments of its super type.");
 DEFINE_FLAG(bool, show_internal_names, false,
     "Show names of internal classes (e.g. \"OneByteString\") in error messages "
     "instead of showing the corresponding interface names (e.g. \"String\")");
 DEFINE_FLAG(bool, trace_disabling_optimized_code, false,
     "Trace disabling optimized code.");
 DEFINE_FLAG(bool, throw_on_javascript_int_overflow, false,
     "Throw an exception when the result of an integer calculation will not "
     "fit into a javascript integer.");
+DEFINE_FLAG(bool, use_field_guards, true, "Guard field cids.");
 DEFINE_FLAG(bool, use_lib_cache, true, "Use library name cache");
 
 DECLARE_FLAG(bool, eliminate_type_checks);
 DECLARE_FLAG(bool, enable_type_checks);
 DECLARE_FLAG(bool, error_on_bad_override);
 DECLARE_FLAG(bool, trace_compiler);
 DECLARE_FLAG(bool, trace_deoptimization);
 DECLARE_FLAG(bool, trace_deoptimization_verbose);
 DECLARE_FLAG(bool, verbose_stacktrace);
 DECLARE_FLAG(charp, coverage_dir);
@@ skipping 6700 matching lines @@
     result.set_value(Object::null_instance());
   } else {
     result.SetOffset(0);
   }
   result.set_is_final(is_final);
   result.set_is_const(is_const);
   result.set_owner(owner);
   result.set_token_pos(token_pos);
   result.set_has_initializer(false);
   result.set_is_unboxing_candidate(true);
-  result.set_guarded_cid(kIllegalCid);
-  result.set_is_nullable(false);
+  result.set_guarded_cid(FLAG_use_field_guards ? kIllegalCid : kDynamicCid);
+  result.set_is_nullable(FLAG_use_field_guards ? false : true);
   // Presently, we only attempt to remember the list length for final fields.
-  if (is_final) {
+  if (is_final && FLAG_use_field_guards) {
     result.set_guarded_list_length(Field::kUnknownFixedLength);
   } else {
     result.set_guarded_list_length(Field::kNoFixedLength);
   }
   result.set_dependent_code(Object::null_array());
   return result.raw();
 }
 
 
 
@@ skipping 12066 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart