Add runtime and native entry tags

runtime/bin/io_natives.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.
 
 #include "bin/io_natives.h"
 
 #include <stdlib.h>
 #include <string.h>
 
 #include "bin/builtin.h"
@@ skipping 106 matching lines @@
   for (int i = 0; i < num_entries; i++) {
     struct NativeEntries* entry = &(IOEntries[i]);
     if (!strcmp(function_name, entry->name_) &&
         (entry->argument_count_ == argument_count)) {
       return reinterpret_cast<Dart_NativeFunction>(entry->function_);
     }
   }
   return NULL;
 }
 
+
+const uint8_t* IONativeSymbol(Dart_NativeFunction nf) {
+  int num_entries = sizeof(IOEntries) / sizeof(struct NativeEntries);
+  for (int i = 0; i < num_entries; i++) {
+    struct NativeEntries* entry = &(IOEntries[i]);
+    if (reinterpret_cast<Dart_NativeFunction>(entry->function_) == nf) {
+      return reinterpret_cast<const uint8_t*>(entry->name_);
+    }
+  }
+  return NULL;
+}
+
 }  // namespace bin
 }  // namespace dart