gen_snapshot now generates two snapshot buffers, one for the vm isolate

mojo/dart/embedder/snapshot.cc.tmpl

 // 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.
 
 // This file is linked into the dart executable when it has a snapshot
 // linked into it.
 
 #include <inttypes.h>
 #include <stdint.h>
 #include <stddef.h>
 
 namespace mojo {
 namespace dart {
 
 // The string on the next line will be filled in with the contents of the
-// generated snapshot binary file.
-// This string forms the content of a snapshot which is loaded in by dart.
-static const uint8_t snapshot_buffer_[] = { % s};
-const uint8_t* snapshot_buffer = snapshot_buffer_;
+// generated snapshot binary file for the vm isolate.
+// This string forms the content of the dart vm isolate snapshot which
+// is loaded into the vm isolate.
+static const uint8_t vm_isolate_snapshot_buffer_[] = { % s};
+const uint8_t* vm_isolate_snapshot_buffer = vm_isolate_snapshot_buffer_;
+
+// The string on the next line will be filled in with the contents of the
+// generated snapshot binary file for a regular dart isolate.
+// This string forms the content of a regular dart isolate snapshot which
+// is loaded into an isolate when it is created.
+static const uint8_t isolate_snapshot_buffer_[] = { % s};
+const uint8_t* isolate_snapshot_buffer = isolate_snapshot_buffer_;
 
 }  // namespace dart
 }  // namespace mojo