Make the values of Platform.executable and Platform.script available to all isolates

sdk/lib/io/platform_impl.dart

Index: sdk/lib/io/platform_impl.dart
diff --git a/sdk/lib/io/platform_impl.dart b/sdk/lib/io/platform_impl.dart
index b9bae7849572b90fd9c643abb296a6cb40e50b33..72e92a64c80606db69ca9b1114c3307f65ff14b3 100644
--- a/sdk/lib/io/platform_impl.dart
+++ b/sdk/lib/io/platform_impl.dart
@@ -9,6 +9,7 @@ class _Platform {
   external static String _pathSeparator();
   external static String _operatingSystem();
   external static _localHostname();
+  external static _executable();
   external static _environment();
   external static String _version();
 
@@ -25,6 +26,11 @@ class _Platform {
     }
   }
 
+  static String get executable {

[Bill Hesse, 2013/08/07 13:39:44]

_executable() can never return null.  It returns a string, or it throws an
exception.

It almost seems like we could do
static String executable = _executable();
except that we may have no guarantee that the initialization is lazy on
platforms where _executable() throws an exception.

So, unless we cache explicitly with
get executable {
  if (executableCache == null) {
    executableCache = _executable();
  }
  return executableCache;
}

we might as well just call _executable() from Platform.executable.  This
function does nothing.

[Søren Gjesse, 2013/08/07 14:37:46]

Initially I was expecting to handle NULL, but it can never happen. Changed to be
just

static String executable = _executable();

+    var executable = _executable();
+    return executable != null ? executable : "";
+  }
+
   static Map<String, String> get environment {
     var env = _environment();
     if (env is OSError) {