Add PRESUBMIT.py to tools/sharding_supervisor/

tools/sharding_supervisor/stdio_buffer.py

 # Copyright (c) 2012 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.
 """Syncronized Standard IO Linebuffer implemented with cStringIO."""
 
 import cStringIO
-import os
-import sys
 import threading
 import Queue
 
 
 class StdioBuffer(object):
   def __init__(self, shard):
     self.queue = Queue.Queue()
     self.completed = 0
     self.shard = shard
 
   def _pipe_handler(self, system_pipe, program_pipe):
     """Helper method for collecting stdio output.  Output is collected until
     a newline is seen, at which point an event is triggered and the line is
     pushed to a buffer as a (stdio, line) tuple."""
-    buffer = cStringIO.StringIO()
+    buf = cStringIO.StringIO()

[csharp, 2013/01/29 01:34:18]

Why buffer to buf?

     pipe_running = True
     while pipe_running:
       char = program_pipe.read(1)
       if not char and self.shard.poll() is not None:
         pipe_running = False
-      buffer.write(char)
+      buf.write(char)
       if char == '\n' or not pipe_running:
-        line = buffer.getvalue()
+        line = buf.getvalue()
         if line:
           self.queue.put((system_pipe, line))
         if not pipe_running:
           self.queue.put((system_pipe, None))
-        buffer.close()
-        buffer = cStringIO.StringIO()
+        buf.close()
+        buf = cStringIO.StringIO()
 
   def handle_pipe(self, system_pipe, program_pipe):
     t = threading.Thread(target=self._pipe_handler, args=[system_pipe,
                                                           program_pipe])
     t.start()
     return t
 
   def readline(self):
     """Emits a tuple of (sys.stderr, line), (sys.stdout, line), or (None, None)
     if the process has finished.  This is a blocking call."""
     while True:
       (pipe, line) = self.queue.get(True)
       if line:
         return (pipe, line)
       self.completed += 1
       if self.completed >= 2:
         return (None, None)