Add Directory.createTemp() to asynchronously create a temporary directory.

runtime/bin/directory.dart

Index: runtime/bin/directory.dart
diff --git a/runtime/bin/directory.dart b/runtime/bin/directory.dart
index a99de599780586b247cd411dc007b0bf68f39933..f1e55fec22a46b79e0652fb0e11038647ab4a932 100644
--- a/runtime/bin/directory.dart
+++ b/runtime/bin/directory.dart
@@ -22,6 +22,17 @@ interface Directory factory _Directory {
   void createSync();
 
   /**
+   * Creates a temporary directory with a name based on this name.
+   * This name is used as a template, and must contain consecutive
+   * 'X' characters, which will be replaced to create a uniqe directory name.

[Mads Ager (google), 2011/11/18 09:50:45]

unique?

Is there a requirement on the number of 'X' characters?

I'm not sure about the interface here. I think it might be more natural to have
the createTemp call actually modify this directory object replacing the name
with the name of the freshly created directory. Otherwise you have this extra
directory object that you don't need for anything.

var temp = new Directory("nameXXXXXX");
temp.createTempSync();
// use temp.

var temp = new Directory("nameXXXXXX");
temp.createTempHandler = () {
  // use temp.
}
temp.createTemp();

[Bill Hesse, 2011/11/21 15:48:41]

Changed.  The template is the path, and the unique characters are added at the
end.

On 2011/11/18 09:50:45, Mads Ager wrote:

+   * The new directory object will be passed to the provided callback,
+   * once it is created.  The original directory object is unchanged.
+   * Throw an exception if the temporary directory cannot be created.
+   * The new directory inherits all handlers from the template directory.
+   */
+  void createTemp(void createdHandler(Directory tempDir));

[Mads Ager (google), 2011/11/18 09:50:45]

Please follow the style in the rest of the file and have the createTempHandler
on the object and not in the function. We can change that at some point if we
want to, but let's keep it consistent for now.

Also, there should be a Sync version as well. However, you can leave that for a
separate change (we need async version of create, exists and delete as well).
Have a look at File to see how we have provided both there.

+
+  /**
    * Deletes the directory with this name. Throws an exception
    * if the directory is not empty or if deletion failed.
    */