Clean and create output directory when generating docs.

frog/file_system_dom.dart

Index: frog/file_system_dom.dart
diff --git a/frog/file_system_dom.dart b/frog/file_system_dom.dart
index c245edcb062e3310d041eac99ec1b336eebeba26..b6e8baaa1d3b3d40015e784905ead53545668bcd 100644
--- a/frog/file_system_dom.dart
+++ b/frog/file_system_dom.dart
@@ -68,4 +68,12 @@ class DomFileSystem implements FileSystem {
 
   // Note: this is not a perf nightmare only because of caching.
   bool fileExists(String filename) => readAll(filename) != null;
+
+  void createDirectory(String path, [bool recursive = false]) {
+    throw 'createDirectory() is not implemented by DomFileSystem yet.';

[Jacob, 2011/11/16 19:59:30]

perhaps add a TODO for each of these methods?
Also, no need to include DomFileSystem in the error as that's obvious for the
callstack if someone cares.  Same for the method name itself.

[Bob Nystrom, 2011/11/17 20:44:21]

Done.

+  }
+
+  void removeDirectory(String path, [bool recursive = false]) {
+    throw 'removeDirectory() is not implemented by DomFileSystem yet.';
+  }
 }