sandwich: Make metrics extraction more customizable.

tools/android/loading/sandwich_runner.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 os
 import shutil
 import sys
 import tempfile
 
@@ skipping 236 matching lines @@
         for repeat_id in xrange(self.repeat):
           self._RunUrl(run_id=repeat_id)
     finally:
       if self._local_cache_directory_path:
         shutil.rmtree(self._local_cache_directory_path)
         self._local_cache_directory_path = None
     if self.cache_operation == CacheOperation.SAVE:
       self._PullCacheFromDevice()
 
     self._chrome_ctl = None
+
+
+def WalkRepeatedRuns(runner_output_dir):
+  """Yields unordered (repeat id, path of the repeat directory).
+
+  Args:
+    runner_output_dir: Same as for SandwichRunner.output_dir.
+  """
+  repeated_run_count = 0
+  for node_name in os.listdir(runner_output_dir):
+    repeat_dir = os.path.join(runner_output_dir, node_name)
+    if not os.path.isdir(repeat_dir):
+      continue
+    try:
+      repeat_id = int(node_name)
+    except ValueError:
+      continue
+    yield repeat_id, repeat_dir
+    repeated_run_count += 1
+  assert repeated_run_count > 0, ('Error: not a sandwich runner output '
+                                  'directory: {}').format(runner_output_dir)