Port perf.py's _LoginToGoogleAccount to chrome_remote_control

tools/chrome_remote_control/chrome_remote_control/credentials_backend.py

Index: tools/chrome_remote_control/chrome_remote_control/credentials_backend.py
diff --git a/tools/chrome_remote_control/chrome_remote_control/credentials_backend.py b/tools/chrome_remote_control/chrome_remote_control/credentials_backend.py
new file mode 100644
index 0000000000000000000000000000000000000000..c446e184d684b4e7657b81df283945f9c8a1e7ec
--- /dev/null
+++ b/tools/chrome_remote_control/chrome_remote_control/credentials_backend.py
@@ -0,0 +1,48 @@
+# 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.
+
+from chrome_remote_control import util
+
+class CredentialsBackend(object):
+  label = None
+
+  def __init__(self, browser_credentials):
+    self.browser_credentials = browser_credentials
+
+  def LoginNeeded(self, tab):
+    raise NotImplementedError()
+
+  def LoginNoLongerNeeded(self, tab):
+    raise NotImplementedError()
+
+  @staticmethod
+  def SubmitForm(form_id, tab):
+    """Submits the given form ID, and returns after it has been submitted.
+
+    Args:
+      form_id: the id attribute of the form to submit.
+    """
+    js = 'document.getElementById("%s").submit();' % form_id
+
+    tab.runtime.Execute(js)
+
+  @staticmethod
+  def WaitForFormToLoad(form_id, tab):
+    def IsFormLoaded():
+      return tab.runtime.Evaluate(
+          'document.querySelector("#%s")!== null' % form_id)
+
+    # Wait until the form is submitted and the page completes loading.
+    util.WaitFor(lambda: IsFormLoaded(), 60) # pylint: disable=W0108
+
+  @classmethod
+  def SubmitFormAndWait(cls, form_id, tab):
+    cls.SubmitForm(form_id, tab)
+
+    def IsLoginStillHappening():
+      return tab.runtime.Evaluate(
+          'document.querySelector("#%s")!== null' % form_id)
+
+    # Wait until the form is submitted and the page completes loading.
+    util.WaitFor(lambda: not IsLoginStillHappening(), 60)