dart:io | Remove deprecated behavior of Directory('').createTemp, replaced by Directory.systemTemp.

sdk/lib/io/directory_impl.dart

Index: sdk/lib/io/directory_impl.dart
diff --git a/sdk/lib/io/directory_impl.dart b/sdk/lib/io/directory_impl.dart
index 288364868df2b194827bd594a157b9ecb1755f04..c8402676638cb40984bf9428ec0f359480025061 100644
--- a/sdk/lib/io/directory_impl.dart
+++ b/sdk/lib/io/directory_impl.dart
@@ -155,9 +155,9 @@ class _Directory extends FileSystemEntity implements Directory {
   Future<Directory> createTemp([String prefix]) {
     if (prefix == null) prefix = '';
     if (path == '') {
-      return systemTemp.createTemp(prefix);
-      // TODO(13720): On Oct 18, 2013, replace this with
-      // an error.  createTemp cannot be called on a Directory with empty path.
+      throw new ArgumentError(
+          "Directory.createTemp called with an empty path. "
+          "To use the system temp directory, use Directory.systemTemp");
     }
     String fullPrefix;
     if (path.endsWith('/') || (Platform.isWindows && path.endsWith('\\'))) {
@@ -178,9 +178,9 @@ class _Directory extends FileSystemEntity implements Directory {
   Directory createTempSync([String prefix]) {
     if (prefix == null) prefix = '';
     if (path == '') {
-      return systemTemp.createTempSync(prefix);
-      // TODO(13720): On Oct 18, 2013, replace this with
-      // an error.  createTemp cannot be called on a Directory with empty path.
+      throw new ArgumentError(
+          "Directory.createTemp called with an empty path. "
+          "To use the system temp directory, use Directory.systemTemp");
     }
     String fullPrefix;
     if (path.endsWith('/') || (Platform.isWindows && path.endsWith('\\'))) {