Add FLAG_trace_maps

src/runtime/runtime-debug.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/arguments.h"
 #include "src/debug.h"
 #include "src/deoptimizer.h"
@@ skipping 2065 matching lines @@
 
   // Clear the oneshot breakpoints so that the debugger does not step further.
   isolate->debug()->ClearStepping();
   return result;
 }
 
 
 static Handle<JSObject> NewJSObjectWithNullProto(Isolate* isolate) {
   Handle<JSObject> result =
       isolate->factory()->NewJSObject(isolate->object_function());
-  Handle<Map> new_map = Map::Copy(Handle<Map>(result->map()));
+  Handle<Map> new_map =
+      Map::Copy(Handle<Map>(result->map()), "ObjectWithNullProto");
   new_map->set_prototype(*isolate->factory()->null_value());
   JSObject::MigrateToMap(result, new_map);
   return result;
 }
 
 
 // Evaluate a piece of JavaScript in the context of a stack frame for
 // debugging.  Things that need special attention are:
 // - Parameters and stack-allocated locals need to be materialized.  Altered
 //   values need to be written back to the stack afterwards.
@@ skipping 624 matching lines @@
   return Smi::FromInt(isolate->debug()->is_active());
 }
 
 
 RUNTIME_FUNCTION(RuntimeReference_DebugBreakInOptimizedCode) {
   UNIMPLEMENTED();
   return NULL;
 }
 }
 }  // namespace v8::internal