Work on blink GN bindings

Source/modules/modules.gni

 # 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.
 
 # This file is gn GN version of modules.gypi. Note that all file lists are
 # relative to the source root.
 _gypi = exec_script(
     "//build/gypi_to_gn.py",
     [ rebase_path("modules.gypi"),
       "--replace=<(SHARED_INTERMEDIATE_DIR)=$root_gen_dir"],
     "scope",
     [ "modules.gypi" ])
 
 _tmp_modules_idl_files = _gypi.modules_idl_files
 # modules_idl_files has a magic variable in it that is an embedder hook,
 # remove that since it's not a file (need to do this before rebasing).
 _tmp_modules_idl_files -= [
   "<@(extra_blink_module_idl_files)",
 ]
-modules_idl_files = rebase_path(_tmp_modules_idl_files, "//")
+modules_idl_files = get_path_info(_tmp_modules_idl_files, "abspath")
 
 # 'partial interface' or target (right side of) 'implements'
 modules_dependency_idl_files =
-  rebase_path(_gypi.modules_dependency_idl_files, "//")
+  get_path_info(_gypi.modules_dependency_idl_files, "abspath")
 
-# Relative to the modules directory.
-modules_event_idl_files = _gypi.modules_event_idl_files
+modules_event_idl_files =
+  get_path_info(_gypi.modules_event_idl_files, "abspath")
 
 # interfaces that inherit from Event
-generated_modules_files = rebase_path(_gypi.generated_modules_files, "//")
+generated_modules_files =
+  get_path_info(_gypi.generated_modules_files, "abspath")
 
 # Remove GYP variables from the list (need to do this before rebasing).
 _tmp_modules_files = _gypi.modules_files
 _tmp_modules_files -= [
   "<@(extra_blink_module_files)",
   "<@(generated_modules_files)",
 ]
-modules_files = rebase_path(_tmp_modules_files, "//")
+modules_files = get_path_info(_tmp_modules_files, "abspath")
 modules_files += generated_modules_files  # Account for GYP var expansion.
 
 # 'partial interface' or target (right side of) 'implements'
 modules_testing_dependency_idl_files =
-  rebase_path(_gypi.modules_testing_dependency_idl_files, "//")
+  get_path_info(_gypi.modules_testing_dependency_idl_files, "abspath")
 
-# Relative to the modules dir.
-modules_testing_files = _gypi.modules_testing_files
-modules_unittest_files = _gypi.modules_unittest_files
+modules_testing_files = get_path_info(_gypi.modules_testing_files, "abspath")
+modules_unittest_files = get_path_info(_gypi.modules_unittest_files, "abspath")
+
+blink_modules_output_dir = "$root_gen_dir/blink/modules"