Implement spawnUri from dart:isolate. This function allows us to

runtime/vm/benchmark_test.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 VM_BENCHMARK_TEST_H_
 #define VM_BENCHMARK_TEST_H_
 
 #include "include/dart_api.h"
 
 #include "vm/dart.h"
@@ skipping 39 matching lines @@
   }
 
   // Accessors.
   const char* name() const { return name_; }
   void set_score(intptr_t value) { score_ = value; }
   intptr_t score() const { return score_; }
   Isolate* isolate() const { return reinterpret_cast<Isolate*>(isolate_); }
 
   Dart_Isolate CreateIsolate(uint8_t* buffer) {
     char* err = NULL;
-    isolate_ = Dart_CreateIsolate(NULL, buffer, NULL, &err);
+    isolate_ = Dart_CreateIsolate(NULL, NULL, buffer, NULL, &err);
     EXPECT(isolate_ != NULL);
     free(err);
     return isolate_;
   }
 
   void Run() { (*run_)(this); }
   void RunBenchmark();
 
   static void RunAll(const char* executable);
   static void SetExecutable(const char* arg) { executable_ = arg; }
@@ skipping 30 matching lines @@
 
  private:
   Benchmark* benchmark_;
 
   DISALLOW_COPY_AND_ASSIGN(BenchmarkIsolateScope);
 };
 
 }  // namespace dart
 
 #endif  // VM_BENCHMARK_TEST_H_