Remove all unused variables.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/views/metered_stream.py

 # Copyright (C) 2010, 2012 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 97 matching lines @@
 
         # This is the easiest way to make sure a byte stream is printable as ascii
         # with all non-ascii characters replaced.
         uni_msg = msg if isinstance(msg, unicode) else msg.decode('ascii', errors='replace')
         self._stream.write(uni_msg.encode('ascii', errors='replace'))
 
     def writeln(self, txt, now=None, pid=None):
         self.write(self._ensure_newline(txt), now, pid)
 
     def _erase_last_partial_line(self):
-        num_chars = len(self._last_partial_line)
         self._stream.write(self._erasure(self._last_partial_line))
         self._last_partial_line = ''
 
     def flush(self):
         if self._last_partial_line:
             self._stream.write('\n')
             self._last_partial_line = ''
             self._stream.flush()
 
     def number_of_columns(self):
         return self._number_of_columns
 
 
 class _LogHandler(logging.Handler):
 
     def __init__(self, meter):
         logging.Handler.__init__(self)
         self._meter = meter
         self.name = LOG_HANDLER_NAME
 
     def emit(self, record):
         self._meter.writeln(record.getMessage(), record.created, record.process)