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

runtime/bin/main.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 <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 
 #include "include/dart_api.h"
 #include "include/dart_tools_api.h"
@@ skipping 1279 matching lines @@
   }
 
   void* read_only_buffer =
       file->Map(File::kReadOnly, vmisolate_position,
                 instructions_position - vmisolate_position);
   if (read_only_buffer == NULL) {
     Log::PrintErr("Failed to memory map snapshot\n");
     Platform::Exit(kErrorExitCode);
   }
 
-  *vmisolate_buffer = reinterpret_cast<const uint8_t*>(read_only_buffer) +
-                      (vmisolate_position - vmisolate_position);
+  if (vmisolate_size != 0) {
+    *vmisolate_buffer = reinterpret_cast<const uint8_t*>(read_only_buffer) +
+                        (vmisolate_position - vmisolate_position);
+  }
   *isolate_buffer = reinterpret_cast<const uint8_t*>(read_only_buffer) +
                     (isolate_position - vmisolate_position);
   if (rodata_size == 0) {
     *rodata_buffer = NULL;
   } else {
     *rodata_buffer = reinterpret_cast<const uint8_t*>(read_only_buffer) +
                      (rodata_position - vmisolate_position);
   }
 
   if (instructions_size == 0) {
@@ skipping 188 matching lines @@
 static void GeneratePrecompiledJITSnapshot() {
   uint8_t* vm_isolate_buffer = NULL;
   intptr_t vm_isolate_size = 0;
   uint8_t* isolate_buffer = NULL;
   intptr_t isolate_size = 0;
   uint8_t* instructions_blob_buffer = NULL;
   intptr_t instructions_blob_size = 0;
   uint8_t* rodata_blob_buffer = NULL;
   intptr_t rodata_blob_size = 0;
   Dart_Handle result = Dart_CreateAppJITSnapshot(
-      &vm_isolate_buffer, &vm_isolate_size, &isolate_buffer, &isolate_size,
-      &instructions_blob_buffer, &instructions_blob_size, &rodata_blob_buffer,
-      &rodata_blob_size);
+      &isolate_buffer, &isolate_size, &instructions_blob_buffer,
+      &instructions_blob_size, &rodata_blob_buffer, &rodata_blob_size);
   if (Dart_IsError(result)) {
     ErrorExit(kErrorExitCode, "%s\n", Dart_GetError(result));
   }
   WriteAppSnapshot(snapshot_filename, vm_isolate_buffer, vm_isolate_size,
                    isolate_buffer, isolate_size, instructions_blob_buffer,
                    instructions_blob_size, rodata_blob_buffer,
                    rodata_blob_size);
 }
 #endif  // defined(TARGET_ARCH_X64)
 
@@ skipping 461 matching lines @@
   Platform::Exit(Process::GlobalExitCode());
 }
 
 }  // namespace bin
 }  // namespace dart
 
 int main(int argc, char** argv) {
   dart::bin::main(argc, argv);
   UNREACHABLE();
 }