[headless] Refactor headless devtools client API.

testing/scripts/headless_python_unittests.py

 #!/usr/bin/env python
 # Copyright 2016 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 json
 import os
 import sys
 
 
 import common
 
 
 def main_run(args):
   typ_path = os.path.abspath(os.path.join(
       os.path.dirname(__file__), os.path.pardir, os.path.pardir,
       'third_party', 'typ'))
   _AddToPathIfNeeded(typ_path)
   import typ
 
-  top_level_dir = os.path.join(common.SRC_DIR, 'headless', 'lib', 'browser')
+  top_level_dir = os.path.join(
+      common.SRC_DIR, 'headless', 'lib', 'browser', 'devtools_api')
   with common.temporary_file() as tempfile_path:
     rc = typ.main(
         argv=[],
         top_level_dir=top_level_dir,
         write_full_results_to=tempfile_path,
         coverage_source=[top_level_dir])
 
     with open(tempfile_path) as f:
       results = json.load(f)
 
@@ skipping 17 matching lines @@
   if path not in sys.path:
     sys.path.insert(0, path)
 
 
 if __name__ == '__main__':
   funcs = {
     'run': main_run,
     'compile_targets': main_compile_targets,
   }
   sys.exit(common.run_script(sys.argv[1:], funcs))