Fix Dartium build: Add missing Dart_ExitIsolate before call to Dart_CreateIsolate.

runtime/bin/gen_snapshot.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.
 
 // Generate a snapshot file after loading all the scripts specified on the
 // command line.
 
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
@@ skipping 569 matching lines @@
     // Ensure that we mark all libraries as loaded.
     result = Dart_FinalizeLoading(false);
     CHECK_RESULT(result);
 
     // Prepare for script loading by setting up the 'print' and 'timer'
     // closures and setting up 'package root' for URI resolution.
     result =
         DartUtils::PrepareForScriptLoading(package_root, false, builtin_lib);
     CHECK_RESULT(result);
     Dart_ExitScope();
+    Dart_ExitIsolate();
 
     UriResolverIsolateScope::isolate = isolate;
 
     // Now we create an isolate into which we load all the code that needs to
     // be in the snapshot.
     if (Dart_CreateIsolate(NULL, NULL, NULL, NULL, &error) == NULL) {
       fprintf(stderr, "%s", error);
       free(error);
       exit(255);
     }
@@ skipping 19 matching lines @@
   }
   return 0;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 int main(int argc, char** argv) {
   return dart::bin::main(argc, argv);
 }