Use log prints for simulation tracing and fix --disassemble-stubs.

runtime/vm/thread.cc

 // Copyright (c) 2015, 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/thread.h"
 
 #include "vm/compiler_stats.h"
 #include "vm/dart_api_state.h"
 #include "vm/growable_array.h"
 #include "vm/isolate.h"
@@ skipping 624 matching lines @@
   ASSERT((expr)->IsVMHeapObject());                                            \
   if (object.raw() == expr) return Thread::member_name##offset();
 CACHED_VM_OBJECTS_LIST(COMPUTE_OFFSET)
 #undef COMPUTE_OFFSET
   UNREACHABLE();
   return -1;
 }
 
 
 bool Thread::ObjectAtOffset(intptr_t offset, Object* object) {
+  if (Isolate::Current() == Dart::vm_isolate()) {
+    // --disassemble-stubs runs before all the references through
+    // thread have targets
+    return false;
+  }
+
 #define COMPUTE_OFFSET(type_name, member_name, expr, default_init_value)       \
   if (Thread::member_name##offset() == offset) {                               \
     *object = expr;                                                            \
     return true;                                                               \
   }
 CACHED_VM_OBJECTS_LIST(COMPUTE_OFFSET)
 #undef COMPUTE_OFFSET
   return false;
 }
 
@@ skipping 93 matching lines @@
 
 DisableThreadInterruptsScope::~DisableThreadInterruptsScope() {
   if (thread() != NULL) {
     OSThread* os_thread = thread()->os_thread();
     ASSERT(os_thread != NULL);
     os_thread->EnableThreadInterrupts();
   }
 }
 
 }  // namespace dart