Support 'dart.library.X' env variables in the VM.

runtime/lib/bool.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 "vm/bootstrap_natives.h"
 
 #include "include/dart_api.h"
 #include "vm/dart_entry.h"
 #include "vm/dart_api_impl.h"
 #include "vm/exceptions.h"
 #include "vm/isolate.h"
 #include "vm/native_entry.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/symbols.h"
 
 namespace dart {
 
 DEFINE_NATIVE_ENTRY(Bool_fromEnvironment, 3) {
   GET_NON_NULL_NATIVE_ARGUMENT(String, name, arguments->NativeArgAt(1));
   GET_NATIVE_ARGUMENT(Bool, default_value, arguments->NativeArgAt(2));
   // Call the embedder to supply us with the environment.
   const String& env_value =
-      String::Handle(Api::CallEnvironmentCallback(thread, name));
+      String::Handle(Api::GetEnvironmentValue(thread, name));
   if (!env_value.IsNull()) {
     if (Symbols::True().Equals(env_value)) {
       return Bool::True().raw();
     }
     if (Symbols::False().Equals(env_value)) {
       return Bool::False().raw();
     }
   }
   return default_value.raw();
 }
 
 }  // namespace dart