[Predator] Add TouchCrashedFileMetaFeature.

appengine/findit/crash/crash_util.py

Index: appengine/findit/crash/crash_util.py
diff --git a/appengine/findit/crash/crash_util.py b/appengine/findit/crash/crash_util.py
index a17a4e503461d1352041401a2f587e16176fe599..56947a5436ef37a07fea6e37489b955bd51e4354 100644
--- a/appengine/findit/crash/crash_util.py
+++ b/appengine/findit/crash/crash_util.py
@@ -23,6 +23,12 @@ def IsSameFilePath(path_1, path_2):
   Returns:
     Boolean, True if it they are thought to be a same path, False otherwise.
   """
+  if not path_1 and not path_2:

[Martin Barbella, 2017/01/24 18:52:53]

We're only worried about None here, right? I don't necessarily think it's worth
it to handle this here at all, but you could simplify this to something like:

if not path_1 or not path_2:
  return path_1 == path_2

The current approach is a bit more robust if we care about returning true for ''
and None, I suppose, but in that case I'd assume something has gone horribly
wrong.

All of that said, This approach feels like it has the potential to hide subtle
bugs. We don't usually want these paths to be None, right? Unless it complicates
things further, I'd prefer cleaning up the call-sites and adding:

assert path_1 is not None
assert path_2 is not None

[Sharu Jiang, 2017/01/24 19:43:11]

Actually it's possible that a path is None, we are using
``touched_file_info.new_path`` to compare, so if the touched file is deleted,
the new_path is None, the ``IsSameFilePath`` should return False.

+    return True
+
+  if not path_1 or not path_2:
+    return False
+
   # TODO(katesonia): Think of better way to determine whether 2 paths are the
   # same or not.
   path_parts_1 = path_1.lower().split('/')