[Predator] Move ``FilterStackBuffer`` from stack parser to ``AddFilteredStack`` of stacktrace buffe…

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):
 
-  @staticmethod
-  def FilterStackBuffer(stack_buffer, filters):
-    """Builds stack buffer to keep all the Callstack inforamtion and metadata.
-
-    Filter stack buffers and cache all the metadata for later use in
-    ``BuildStackTrace``.
-
-    Args:
-      stack_buffer (CallStackBuffer): callstack buffer to be filtered.
-      filters (list): List of Filter objs, each Filter obj is callable and takes
-        stack_buffer as the only parameter.
-
-    Returns:
-      A new ``CallStackBuffer`` instance, None when all the frames of the
-      stack buffer are filtered.
-    """
-    # If the callstack is the initial one (infinte priority) or empty, return
-    # None.
-    if math.isinf(stack_buffer.priority) or not stack_buffer.frames:
-      return None
-
-    for stack_filter in filters:
-      stack_buffer = stack_filter(stack_buffer)
-      if not stack_buffer:
-        return None
-
-    return stack_buffer
-
   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()