Add member localHostname() to the Dart IO Platform class.

runtime/bin/platform.cc

 // Copyright (c) 2011, 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/file.h"
 #include "bin/platform.h"
 #include "include/dart_api.h"
 
 
 void FUNCTION_NAME(Platform_NumberOfProcessors)(Dart_NativeArguments args) {
   Dart_EnterScope();
   Dart_SetReturnValue(args, Dart_NewInteger(Platform::NumberOfProcessors()));
   Dart_ExitScope();
 }
 
 
 void FUNCTION_NAME(Platform_OperatingSystem)(Dart_NativeArguments args) {
   Dart_EnterScope();
   Dart_SetReturnValue(args, Dart_NewString(Platform::OperatingSystem()));
   Dart_ExitScope();
 }
 
 
 void FUNCTION_NAME(Platform_PathSeparator)(Dart_NativeArguments args) {
   Dart_EnterScope();
   Dart_SetReturnValue(args, Dart_NewString(File::PathSeparator()));
   Dart_ExitScope();
 }
+
+
+void FUNCTION_NAME(Platform_LocalHostname)(Dart_NativeArguments args) {
+  Dart_EnterScope();
+  const intptr_t HOSTNAME_LENGTH = 256;
+  char hostname[HOSTNAME_LENGTH];
+  if (Platform::LocalHostname(hostname, HOSTNAME_LENGTH)) {
+    Dart_SetReturnValue(args, Dart_NewString(hostname));
+  } else {
+    Dart_SetReturnValue(args, DartUtils::NewDartOSError());
+  }
+  Dart_ExitScope();
+}