Remove legacy restart code

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, 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 "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
 #include "lib/stacktrace.h"
@@ skipping 791 matching lines @@
   }
   return Api::ClassId(object) == kLanguageErrorCid;
 }
 
 
 DART_EXPORT bool Dart_IsFatalError(Dart_Handle object) {
   return Api::ClassId(object) == kUnwindErrorCid;
 }
 
 
-DART_EXPORT bool Dart_IsVMRestartRequest(Dart_Handle handle) {
-  DARTSCOPE(Thread::Current());
-  const Object& obj = Object::Handle(Z, Api::UnwrapHandle(handle));
-  return (obj.IsUnwindError() && UnwindError::Cast(obj).is_vm_restart());
-}
-
-
 DART_EXPORT const char* Dart_GetError(Dart_Handle handle) {
   API_TIMELINE_DURATION;
   DARTSCOPE(Thread::Current());
   const Object& obj = Object::Handle(Z, Api::UnwrapHandle(handle));
   return GetErrorString(T, obj);
 }
 
 
 DART_EXPORT bool Dart_ErrorHasException(Dart_Handle handle) {
   DARTSCOPE(Thread::Current());
@@ skipping 6012 matching lines @@
 }
 
 
 DART_EXPORT void Dart_DumpNativeStackTrace(void* context) {
 #ifndef PRODUCT
   Profiler::DumpStackTrace(context);
 #endif
 }
 
 }  // namespace dart