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

tools/list_dart_files.py

Index: tools/list_dart_files.py
diff --git a/tools/list_dart_files.py b/tools/list_dart_files.py
index 39ab36555cc4d0ac258fc5b7244a77f43ac1b376..60d2295652e1ea38e99094624bfd21cf3266bcfc 100755
--- a/tools/list_dart_files.py
+++ b/tools/list_dart_files.py
@@ -16,8 +16,6 @@ import sys
 
 def main(argv):
   directory = argv[1]
-  if not os.path.isabs(directory):
-    directory = os.path.realpath(directory)
 
   pattern = None
   if len(argv) > 2:
@@ -36,7 +34,7 @@ def main(argv):
 
     for filename in files:
       if filename.endswith('.dart') and not filename.endswith('_test.dart'):
-        fullname = os.path.join(directory, root, filename)
+        fullname = os.path.relpath(os.path.join(root, filename))
         fullname = fullname.replace(os.sep, '/')
         print fullname