[Predator] Make ``CallStackDetector`` return a namedtuple.

appengine/findit/crash/clusterfuzz_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 logging
 import re
 
 from crash import callstack_detectors
 from crash.callstack_filters import FilterFramesAfterBlinkGeneratedCode
 from crash.callstack_filters import FilterJavaJreSdkFrames
@@ skipping 86 matching lines @@
                     signature or '', job_type)
       return None
 
     # Initial background callstack which is not to be added into Stacktrace.
     stack_buffer = CallStackBuffer()
     # Reset both stacktrace and callstack flags.
     self.flag_manager.ResetAllFlags()
     for line in stacktrace_string.splitlines():
       # Note, some flags like is_first_stack may be changed inside of stack
       # detector.
-      is_new_callstack, priority, format_type, language_type, metadata = (
-          stack_detector.IsStartOfNewCallStack(line, flags=self.flag_manager))
+      start_of_callstack = stack_detector(line)
 
-      if is_new_callstack:
+      if start_of_callstack:
         stacktrace_buffer.AddFilteredStack(
             self.UpdateMetadataWithFlags(stack_buffer))
-
         # Create new stack and reset callstack scope flags.
-        stack_buffer = CallStackBuffer(priority=priority,
-                                       format_type=format_type,
-                                       language_type=language_type,
-                                       metadata=metadata)
+        stack_buffer = CallStackBuffer.FromStartOfCallStack(start_of_callstack)
         self.flag_manager.ResetGroupFlags(CALLSTACK_FLAG_GROUP)
       else:
         frame = StackFrame.Parse(stack_buffer.language_type,
                                  stack_buffer.format_type, line, deps,
                                  len(stack_buffer.frames))
         if frame is not None:
           stack_buffer.frames.append(frame)
         # Turn on flags if condition met.
         self.flag_manager.ConditionallyTurnOnFlags(line)
 
     # Add the last stack to stacktrace.
     stacktrace_buffer.AddFilteredStack(
         self.UpdateMetadataWithFlags(stack_buffer))
     return stacktrace_buffer.ToStacktrace()