Have shelldb and skydb automatically download assets for you

sky/tools/skydb

 #!/usr/bin/env python
 # 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.
 
 from skypy.skyserver import SkyServer
 import argparse
 import json
 import logging
 import os
@@ skipping 40 matching lines @@
         '--list', '--short'
     ]
     config = {}
     for line in subprocess.check_output(gn_cmd).strip().split('\n'):
         # FIXME: This doesn't handle = in values.
         key, value = line.split(' = ')
         config[key] = value
     return config
 
 
+def ensure_assets_are_downloaded(build_dir):
+    sky_pkg_dir = os.path.join(build_dir, 'gen', 'dart-pkg', 'sky')
+    sky_pkg_lib_dir = os.path.join(sky_pkg_dir, 'lib')
+    sky_icons_dir = \
+        os.path.join(sky_pkg_lib_dir, 'assets', 'material-design-icons')
+    if not os.path.isdir(sky_icons_dir):
+        logging.info('NOTE: sky/assets/material-design-icons missing, '
+                     'Running `download_material_design_icons` for you.')
+        subprocess.check_call(
+            [os.path.join(sky_pkg_lib_dir, 'download_material_design_icons')])
+
 class SkyDebugger(object):
     def __init__(self):
         self.pids = {}
         self.paths = None
 
     def _server_root_for_url(self, url_or_path):
         path = os.path.abspath(url_or_path)
         if os.path.commonprefix([path, SRC_ROOT]) == SRC_ROOT:
             server_root = SRC_ROOT
         else:
@@ skipping 102 matching lines @@
     def start_command(self, args):
         # FIXME: Lame that we use self for a command-specific variable.
         self.paths = self._create_paths_for_build_dir(args.build_dir)
         self.stop_command(None) # Quit any existing process.
 
         # FIXME: This is probably not the right way to compute is_android
         # from the build directory?
         gn_args = gn_args_from_build_dir(self.paths.build_dir)
         is_android = 'android_sdk_version' in gn_args
 
+        ensure_assets_are_downloaded(args.build_dir)
+
         shell_found = True
         if is_android:
             apk_path = os.path.join(self.paths.build_dir, 'apks', ANDROID_APK_NAME)
             if not os.path.exists(apk_path):
                 print "%s not found in build_dir '%s'" % \
                     (ANDROID_APK_NAME, os.path.join(args.build_dir, 'apks'))
                 shell_found = False
         elif not os.path.exists(self.paths.mojo_shell_path):
             print "mojo_shell not found in build_dir '%s'" % args.build_dir
             shell_found = False
@@ skipping 424 matching lines @@
         load_parser.set_defaults(func=self.load_command)
 
         args = parser.parse_args()
         args.func(args)
 
         self._write_pid_file(PID_FILE_PATH, self.pids)
 
 
 if __name__ == '__main__':
     SkyDebugger().main()