[Predator] Add Clusterfuzz stacktrace parser.

appengine/findit/crash/stacktrace_parser.py

 # Copyright 2016 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.
 
 import math
 
 from crash.stacktrace import CallStackBuffer
 from crash.stacktrace import Stacktrace
 
 
 class StacktraceParser(object):
 
   def Parse(self, stacktrace_string, deps, signature=None, top_n_frames=None):
     """Parses stacktrace_string into ``Stacktrace`` instance.
 
     Args:
       stacktrace_string (str): Raw string to be parsed.
       deps (dict): Dict mapping repository path to ``Dependency`` instance, used
         to resolve dependency of frames.
       signature (str): Signature is used to mark signature callstack, signature
         callstack is the crash stack that causing the crash.
       top_n_frames (int): Number of top frames to be keep in a callstack.
     """
     raise NotImplementedError()
-
-  def _IsStartOfNewCallStack(self, line):
-    """Determines whether a line is the start of a new callstack or not."""
-    raise NotImplementedError()