Implement spawnFunction from the new isolate api.

runtime/vm/zone.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_ZONE_H_
 #define VM_ZONE_H_
 
 #include "platform/utils.h"
 #include "vm/allocation.h"
 #include "vm/handles.h"
@@ skipping 105 matching lines @@
 
   // Compute the total size of this zone. This includes wasted space that is
   // due to internal fragmentation in the segments.
   intptr_t SizeInBytes() const { return zone_.SizeInBytes(); }
 
   // Make a copy of the string in the zone allocated area.
   char* MakeCopyOfString(const char* str) {
     return zone_.MakeCopyOfString(str);
   }
 
+  // Make a zone-allocated string based on printf format and args.
+  char* PrintToString(const char* format, ...);
+
   VMHandles* handles() { return &handles_; }
 
   void VisitObjectPointers(ObjectPointerVisitor* visitor);
 
  private:
   BaseZone* GetBaseZone() { return &zone_; }
 
   BaseZone zone_;
 
   // Structure for managing handles allocation.
@@ skipping 26 matching lines @@
   }
 
   // Check that the result has the proper alignment and return it.
   ASSERT(Utils::IsAligned(result, kAlignment));
   return result;
 }
 
 }  // namespace dart
 
 #endif  // VM_ZONE_H_