Fix facebook_credentials_backend_unittest on android-content-shell.

tools/telemetry/telemetry/google_credentials_backend.py

Index: tools/telemetry/telemetry/google_credentials_backend.py
diff --git a/tools/telemetry/telemetry/google_credentials_backend.py b/tools/telemetry/telemetry/google_credentials_backend.py
index c41579af50127c905980859f67ba7b576f5b54b3..cab544db34855116eaf6adda95043d9f80b835b1 100644
--- a/tools/telemetry/telemetry/google_credentials_backend.py
+++ b/tools/telemetry/telemetry/google_credentials_backend.py
@@ -6,6 +6,10 @@ from telemetry import form_based_credentials_backend
 
 class GoogleCredentialsBackend(
     form_based_credentials_backend.FormBasedCredentialsBackend):
+  def IsAlreadyLoggedIn(self, tab):
+    return tab.EvaluateJavaScript(
+        'document.getElementById("gb")!== null')
+
   @property
   def credentials_type(self):
     return 'google'
@@ -19,10 +23,6 @@ class GoogleCredentialsBackend(
     return 'gaia_loginform'
 
   @property
-  def already_logged_in_element_id(self):
-    return 'gb'
-
-  @property
   def login_input_id(self):
     return 'Email'