[Android] Extract device blacklisting into its own module.

build/android/pylib/device/device_blacklist.py

+# Copyright 2014 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 json
+import os
+
+from pylib import constants
+_BLACKLIST_JSON = os.path.join(
+    constants.DIR_SOURCE_ROOT,
+    os.environ.get('CHROMIUM_OUT_DIR', 'out'),
+    'bad_devices.json')
+
+def ReadBlacklist():
+  """Reads the blacklist from the _BLACKLIST_JSON file.
+
+  Returns:
+    A list containing bad devices.
+  """
+  if not os.path.exists(_BLACKLIST_JSON):
+    return []
+
+  with open(_BLACKLIST_JSON, 'r') as f:
+    return json.load(f)
+
+
+def WriteBlacklist(blacklist):
+  """Writes the provided blacklist to the _BLACKLIST_JSON file.
+
+  Args:
+    blacklist: list of bad devices to write to the _BLACKLIST_JSON file.
+  """
+  with open(_BLACKLIST_JSON, 'w') as f:
+    json.dump(list(set(blacklist)), f)
+
+
+def ExtendBlacklist(devices):
+  """Adds devices to _BLACKLIST_JSON file.
+
+  Args:
+    devices: list of bad devices to be added to the _BLACKLIST_JSON file.
+  """
+  blacklist = ReadBlacklist()
+  blacklist.extend(devices)
+  WriteBlacklist(blacklist)
+
+
+def ResetBlacklist():
+  """Erases the _BLACKLIST_JSON file if it exists."""
+  if os.path.exists(_BLACKLIST_JSON):
+    os.remove(_BLACKLIST_JSON)
+