Make list_files.py and list_dart_files.py return absolute paths for GN

utils/create_timestamp.gni

Index: utils/create_timestamp.gni
diff --git a/utils/create_timestamp.gni b/utils/create_timestamp.gni
index c579da1e5e3bf9d99b8f8f415eb6c2860507ae29..75ae4cda7a50ca1633d08f0764dd0ba7ba0cb440 100644
--- a/utils/create_timestamp.gni
+++ b/utils/create_timestamp.gni
@@ -7,14 +7,6 @@ _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) {
@@ -23,10 +15,9 @@ template("create_timestamp_file") {
       list_args += [ invoker.pattern ]
     }
     files = exec_script("$_dart_root/tools/list_dart_files.py",
-                        list_args,
+                        [ "absolute" ] + list_args,
                         "list lines")
-    inputs = [ "$_dart_root/tools/list_dart_files.py" ] +
-             rebase_path(files, new_base, current_base)
+    inputs = [ "$_dart_root/tools/list_dart_files.py" ] + files
     outputs = [
       output,
     ]