Port perf.py's _LoginToGoogleAccount to chrome_remote_control

tools/chrome_remote_control/chrome_remote_control/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 chrome_remote_control.google_credentials_backend as \
+    google_credentials_backend
+import logging
+
+class BrowserCredentials(object):
+  def __init__(self):
+    self._credentials_backends = \
+        [google_credentials_backend.GoogleCredentialsBackend()]
+
+  def _GetCredentialsBackend(self, credentials_type):
+    for backend in self._credentials_backends:
+      if credentials_type == backend.label:
+        return backend
+
+  def LoginNeeded(self, credentials_type, tab):
+    backend = self._GetCredentialsBackend(credentials_type)
+    if backend:
+      backend.LoginNeeded(tab)
+    else:
+      logging.warning('Credentials not implemented: "%s"', credentials_type)
+
+  def LoginNoLongerNeeded(self, credentials_type, tab):
+    backend = self._GetCredentialsBackend(credentials_type)
+    if backend:
+      backend.LoginNoLongerNeeded(tab)
+    else:
+      logging.warning('Credentials not implemented: "%s"', credentials_type)