Add skydoc.py, a tool for running dartdoc

sky/tools/skypy/url_mappings.py

+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+
+class URLMappings(object):
+    def __init__(self, src_root, build_dir):
+        self.mappings = {
+            'dart:mojo.internal': os.path.join(src_root, 'mojo/public/dart/sdk_ext/internal.dart'),
+            'dart:sky': os.path.join(build_dir, 'gen/sky/bindings/dart_sky.dart'),
+            'dart:sky.internals': os.path.join(src_root, 'sky/engine/bindings/sky_internals.dart'),
+            'dart:sky_builtin_natives': os.path.join(src_root, 'sky/engine/bindings/builtin_natives.dart'),
+        }
+        self.packages_root = os.path.join(build_dir, 'gen/dart-pkg/packages')
+
+    @property
+    def as_args(self):
+        return map(lambda item: '--url-mapping=%s,%s' % item, self.mappings.items())
+