VM: Fix snapshoting slow-down caused by 99c6a18a1bc2a4f13d8dd027a597fdca0f2d6e0c.

runtime/include/dart_tools_api.h

 // Copyright (c) 2011, 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.
 
 #ifndef RUNTIME_INCLUDE_DART_TOOLS_API_H_
 #define RUNTIME_INCLUDE_DART_TOOLS_API_H_
 
 #include "dart_api.h"
 
 /** \mainpage Dart Tools Embedding API Reference
@@ skipping 888 matching lines @@
 /**
  * A callback which determines whether the file at some url has been
  * modified since some time.  If the file cannot be found, true should
  * be returned.
  */
 typedef bool (*Dart_FileModifiedCallback)(const char* url, int64_t since);
 
 DART_EXPORT Dart_Handle
 Dart_SetFileModifiedCallback(Dart_FileModifiedCallback file_modified_callback);
 
+/**
+ * Returns true if isolate is currently reloading.
+ */
+DART_EXPORT bool Dart_IsReloading();
+
 /*
  * ========
  * Timeline
  * ========
  */
 
 /**
  * Returns a timestamp in microseconds. This timestamp is suitable for
  * passing into the timeline system.
  *
@@ skipping 148 matching lines @@
  * \param start_recording See Dart_EmbedderTimelineStartRecording.
  * \param stop_recording See Dart_EmbedderTimelineStopRecording.
  *
  * NOTE: To avoid races, this should be called before Dart_Initialize.
  */
 DART_EXPORT void Dart_SetEmbedderTimelineCallbacks(
     Dart_EmbedderTimelineStartRecording start_recording,
     Dart_EmbedderTimelineStopRecording stop_recording);
 
 #endif  // RUNTIME_INCLUDE_DART_TOOLS_API_H_