Bring up the service isolate and use it for package resolution in gen_snapshot

runtime/bin/builtin_gen_snapshot.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 <stdio.h>
 #include <string.h>
 
 #include "include/dart_api.h"
 
 #include "bin/builtin.h"
+#include "bin/io_natives.h"
 
 namespace dart {
 namespace bin {
 
 // Lists the native function implementing basic logging facility.
 #define BUILTIN_NATIVE_LIST(V)                                                 \
   V(Builtin_PrintString, 1)
 
 BUILTIN_NATIVE_LIST(DECLARE_FUNCTION);
 
@@ skipping 16 matching lines @@
   ASSERT(auto_setup_scope != NULL);
   *auto_setup_scope = true;
   int num_entries = sizeof(BuiltinEntries) / sizeof(struct NativeEntries);
   for (int i = 0; i < num_entries; i++) {
     struct NativeEntries* entry = &(BuiltinEntries[i]);
     if (!strcmp(function_name, entry->name_) &&
         (entry->argument_count_ == argument_count)) {
       return reinterpret_cast<Dart_NativeFunction>(entry->function_);
     }
   }
-  return NULL;
+  return IONativeLookup(name, argument_count, auto_setup_scope);
 }
 
 
 const uint8_t* Builtin::NativeSymbol(Dart_NativeFunction nf) {
   int num_entries = sizeof(BuiltinEntries) / sizeof(struct NativeEntries);
   for (int i = 0; i < num_entries; i++) {
     struct NativeEntries* entry = &(BuiltinEntries[i]);
     if (reinterpret_cast<Dart_NativeFunction>(entry->function_) == nf) {
       return reinterpret_cast<const uint8_t*>(entry->name_);
     }
   }
-  return NULL;
+  return IONativeSymbol(nf);
 }
 
 
 // Implementation of native functions which are used for some
 // test/debug functionality in standalone dart mode.
 void FUNCTION_NAME(Builtin_PrintString)(Dart_NativeArguments args) {
   Dart_EnterScope();
   intptr_t length = 0;
   uint8_t* chars = NULL;
   Dart_Handle str = Dart_GetNativeArgument(args, 0);
   Dart_Handle result = Dart_StringToUTF8(str, &chars, &length);
   if (Dart_IsError(result)) {
     // TODO(turnidge): Consider propagating some errors here.  What if
     // an isolate gets interrupted by the embedder in the middle of
     // Dart_StringToUTF8?  We need to make sure not to swallow the
     // interrupt.
     fputs(Dart_GetError(result), stdout);
   } else {
     fwrite(chars, sizeof(*chars), length, stdout);
   }
   fputc('\n', stdout);
   fflush(stdout);
   Dart_ExitScope();
 }
 
 }  // namespace bin
 }  // namespace dart