Fix build bot error.

runtime/bin/extensions_win.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 "platform/assert.h"
 #include "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "bin/extensions.h"
 #include "bin/utils.h"
@@ skipping 10 matching lines @@
                                              void** library_handle) {
   ASSERT(library_handle != NULL);
   *library_handle = LoadLibraryW(StringUtilsWin::Utf8ToWide(library_file));
   if (*library_handle == NULL) {
     OSError err;
     return Dart_NewApiError(err.message());
   }
   return Dart_Null();
 }
 
+void* Extensions::LoadExtensionLibrary(const char* library_file) {
+  return LoadLibraryW(StringUtilsWin::Utf8ToWide(library_file));
+}
+
 Dart_Handle Extensions::ResolveSymbol(void* lib_handle,
                                       const char* symbol,
                                       void** init_function) {
   ASSERT(init_function != NULL);
   *init_function = GetProcAddress(
       reinterpret_cast<HMODULE>(lib_handle), symbol);
   if (*init_function == NULL) {
     OSError err;
     return Dart_NewApiError(err.message());
   }
   return Dart_Null();
 }
 
+void* Extensions::ResolveSymbol(void* lib_handle, const char* symbol) {
+  return GetProcAddress(reinterpret_cast<HMODULE>(lib_handle), symbol);
+}
+
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)