When creating a JIT app snapshot, don't recreate the VM isolate snapshot.

runtime/include/dart_api.h

 /*
  * 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.
  */
 
 #ifndef RUNTIME_INCLUDE_DART_API_H_
 #define RUNTIME_INCLUDE_DART_API_H_
 
 /** \mainpage Dart Embedding API Reference
@@ skipping 3267 matching lines @@
  *     same version, must be built in the same DEBUG/RELEASE/PRODUCT mode, must
  *     be targeting the same architecture, and must both be in checked mode or
  *     both in unchecked mode.
  *
  *  The buffers are scope allocated and are only valid until the next call to
  *  Dart_ExitScope.
  *
  * \return A valid handle if no error occurs during the operation.
  */
 DART_EXPORT Dart_Handle
-Dart_CreateAppJITSnapshot(uint8_t** vm_isolate_snapshot_buffer,
-                          intptr_t* vm_isolate_snapshot_size,
-                          uint8_t** isolate_snapshot_buffer,
+Dart_CreateAppJITSnapshot(uint8_t** isolate_snapshot_buffer,
                           intptr_t* isolate_snapshot_size,
                           uint8_t** instructions_blob_buffer,
                           intptr_t* instructions_blob_size,
                           uint8_t** rodata_blob_buffer,
                           intptr_t* rodata_blob_size);
 
 
 /**
  *  Returns whether the VM only supports running from precompiled snapshots and
  *  not from any other kind of snapshot or from source (that is, the VM was
  *  compiled with DART_PRECOMPILED_RUNTIME).
  */
 DART_EXPORT bool Dart_IsPrecompiledRuntime();
 
 
 /**
  *  Print a native stack trace. Used for crash handling.
  */
 DART_EXPORT void Dart_DumpNativeStackTrace(void* context);
 
 #endif /* INCLUDE_DART_API_H_ */ /* NOLINT */