Make sure skyanalyzer uses absolute paths to construct url-mappings for

sky/tools/skyanalyzer

 #!/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.
 
 import argparse
 import os
 import re
 import subprocess
 import sys
@@ skipping 29 matching lines @@
   # dartbug.com/23606
   re.compile(r'^\[warning] Missing concrete implementation of \'RenderObject.toString\''),
 ]
 
 def main():
     parser = argparse.ArgumentParser(description='Sky Analyzer')
     parser.add_argument('--congratulate', action="store_true")
     parser.add_argument('build_dir', type=str)
     parser.add_argument('app_path', type=str)
     args = parser.parse_args()
-    build_dir = args.build_dir
+    build_dir = os.path.abspath(args.build_dir)
     analyzer_path = os.path.join(SRC_ROOT, 'third_party/dart-sdk/dart-sdk/bin/dartanalyzer')
     dart_builtin_natives_path = os.path.join(SRC_ROOT, 'sky/engine/bindings/builtin_natives.dart')
     dart_mojo_internal_path = os.path.join(SRC_ROOT, 'mojo/public/dart/sdk_ext/internal.dart')
     dart_sky_internals_path = os.path.join(SRC_ROOT, 'sky/engine/bindings/sky_internals.dart')
     dart_sky_path = os.path.join(build_dir, 'gen/sky/bindings/dart_sky.dart')
     packages_root = os.path.join(build_dir, 'gen/dart-pkg/packages')
     analyzer_args = [analyzer_path,
         "--url-mapping=dart:mojo.internal,%s" % dart_mojo_internal_path,
         "--url-mapping=dart:sky,%s" % dart_sky_path,
         "--url-mapping=dart:sky.internals,%s" % dart_sky_internals_path,
@@ skipping 12 matching lines @@
           print >> sys.stderr, error
         # Propagate analyzer error code.
         return e.returncode
     # If we do not have any errors left after filtering, return 0.
     if args.congratulate:
       print >> sys.stdout, "No analyzer warnings!"
     return 0
 
 if __name__ == '__main__':
     sys.exit(main())