Add --print_stacktrace_at_api_error.

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/become.h"
@@ skipping 15160 matching lines @@
 
 RawApiError* ApiError::New() {
   ASSERT(Object::api_error_class() != Class::null());
   RawObject* raw = Object::Allocate(ApiError::kClassId,
                                     ApiError::InstanceSize(), Heap::kOld);
   return reinterpret_cast<RawApiError*>(raw);
 }
 
 
 RawApiError* ApiError::New(const String& message, Heap::Space space) {
+#ifndef PRODUCT
+  if (FLAG_print_stacktrace_at_api_error) {
+    OS::PrintErr("ApiError: %s\n", message.ToCString());
+    Profiler::DumpStackTrace(false /* for_crash */);
+  }
+#endif  // !PRODUCT
+
   ASSERT(Object::api_error_class() != Class::null());
   ApiError& result = ApiError::Handle();
   {
     RawObject* raw =
         Object::Allocate(ApiError::kClassId, ApiError::InstanceSize(), space);
     NoSafepointScope no_safepoint;
     result ^= raw;
   }
   result.set_message(message);
   return result.raw();
@@ skipping 7949 matching lines @@
   return UserTag::null();
 }
 
 
 const char* UserTag::ToCString() const {
   const String& tag_label = String::Handle(label());
   return tag_label.ToCString();
 }
 
 }  // namespace dart