Make sure to check for OS errors when constructing Uri.base

runtime/bin/builtin.dart

Index: runtime/bin/builtin.dart
diff --git a/runtime/bin/builtin.dart b/runtime/bin/builtin.dart
index f5eec7e48141bd38a24990e1ce948b38ce9cfe90..3b3a3b00679d845c3147cb381bb2e466ebc2fb2d 100644
--- a/runtime/bin/builtin.dart
+++ b/runtime/bin/builtin.dart
@@ -112,11 +112,9 @@ class _Logger {
 
 _getPrintClosure() => _print;
 
-_getCurrentDirectoryPath() native "Directory_Current";
-
 // Corelib 'Uri.base' implementation.
 Uri _uriBase() {

[Søren Gjesse, 2015/03/04 12:48:13]

We could also do this, if we care about not allocating one Directory object in
this case. I don't think we need to.

  // We are not using Dircetory.current here to avoid allocating a
  // Directory object.
  var result = _getCurrentDirectoryPath();
  if (result is OSError) {
    throw new FileSystemException(
        "Getting current working directory failed", "", result);
  }
  return new Uri.file(result + "/");

[Ivan Posva, 2015/03/04 17:36:25]

By using Directory.current you need to import "dart:io" which we have the goal
to remove. So please use the alternate code. Thanks!

-  return new Uri.file(_getCurrentDirectoryPath() + "/");
+  return new Uri.file(Directory.current.path + "/");
 }
 
 _getUriBaseClosure() => _uriBase;