[telemetry] Move telemetry/core/chrome/ to telemetry/core/backends/chrome/

tools/telemetry/telemetry/core/browser_credentials.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.
+
 import logging
 import json
 import os
 
 from telemetry.core import util
-from telemetry.core.chrome import facebook_credentials_backend
-from telemetry.core.chrome import google_credentials_backend
+from telemetry.core.backends import facebook_credentials_backend
+from telemetry.core.backends import google_credentials_backend
 from telemetry.unittest import options_for_unittests
 
+
 class BrowserCredentials(object):
   def __init__(self, backends = None):
     self._credentials = {}
     self._credentials_path = None
     self._extra_credentials = {}
 
     if backends is None:
       backends = [
         facebook_credentials_backend.FacebookCredentialsBackend(),
         google_credentials_backend.GoogleCredentialsBackend()]
@@ skipping 111 matching lines @@
         Credentials for %s were not found. %i pages will not be tested.
 
         To fix this, either add svn-internal to your .gclient using
         http://goto/read-src-internal, or add your own credentials to:
             %s
         An example credentials file you can copy from is here:
             %s\n""" % (', '.join(missing_credentials),
          num_pages_missing_login,
          ' or '.join(files_to_tweak),
          example_credentials_file))