Revert "Make list_files.py and list_dart_files.py return absolute paths"

utils/create_timestamp.gni

 # Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 _dart_root = rebase_path("..")
 
 template("create_timestamp_file") {
   assert(defined(invoker.path), "Must specify 'path'")
   assert(defined(invoker.output), "Must specify 'output'")
+  new_base = "."
+  if (defined(invoker.new_base)) {
+    new_base = invoker.new_base
+  }
+  current_base = "."
+  if (defined(invoker.current_base)) {
+    current_base = invoker.current_base
+  }
   path = invoker.path
   output = invoker.output
   action(target_name) {
     list_args = [ path ]
     if (defined(invoker.pattern)) {
       list_args += [ invoker.pattern ]
     }
     files = exec_script("$_dart_root/tools/list_dart_files.py",
                         list_args,
                         "list lines")
-    inputs = [ "$_dart_root/tools/list_dart_files.py" ] + files
+    inputs = [ "$_dart_root/tools/list_dart_files.py" ] +
+             rebase_path(files, new_base, current_base)
     outputs = [
       output,
     ]
     script = "$_dart_root/tools/create_timestamp_file.py"
     args = [ rebase_path(output) ]
   }
 }