Address review comments on Options.executable change.

corelib/src/options.dart

Index: corelib/src/options.dart
diff --git a/corelib/src/options.dart b/corelib/src/options.dart
index 4b2994ddfd2570167d305532dffa851d2fd55f91..678de2fbd7565ecf5ba69b309f583e81b91f1b2c 100644
--- a/corelib/src/options.dart
+++ b/corelib/src/options.dart
@@ -19,17 +19,26 @@ interface Options default RuntimeOptions {
    * Returns a list of arguments that have been passed to this isolate. Any
    * modifications to the list will be contained to the options object owning
    * this list.
+   *
+   * If the execution environment does not support [arguments] an empty list
+   * is returned.
    */
   List<String> get arguments();
 
   /**
    * Returns the path of the executable used to run the script in this
    * isolate.
+   *
+   * If the execution environment does not support [executable] an empty
+   * string is returned.
    */
   String get executable();
 
   /**
    * Returns the path of the script being run in this isolate.
+   *
+   * If the executable environment does not support [script] an empty
+   * string is returned.
    */
   String get script();
 }