Fix issue 1278 (#1279)

Author: samtstern

auth/src/main/java/com/firebase/ui/auth/AuthUI.java

@@ -31,6 +31,7 @@
 
 import com.facebook.login.LoginManager;
 import com.firebase.ui.auth.data.model.FlowParameters;
+import com.firebase.ui.auth.data.remote.TwitterSignInHandler;
 import com.firebase.ui.auth.ui.idp.AuthMethodPickerActivity;
 import com.firebase.ui.auth.util.CredentialUtils;
 import com.firebase.ui.auth.util.ExtraConstants;
@@ -276,7 +277,7 @@ public static int getDefaultTheme() {
      * UI-based sign-in flow knowing it is required.
      *
      * @param context        requesting the user be signed in
-     * @param desiredConfigs to use for silent sign in. Only Google and email are currently
+     * @param configs        to use for silent sign in. Only Google and email are currently
      *                       supported, the rest will be ignored.
      * @return a task which indicates whether or not the user was successfully signed in.
      */
@@ -455,6 +456,7 @@ private Task<Void> signOutIdps(@NonNull Context context) {
             LoginManager.getInstance().logOut();
         }
         if (ProviderAvailability.IS_TWITTER_AVAILABLE) {
+            TwitterSignInHandler.initializeTwitter();
             TwitterCore.getInstance().getSessionManager().clearActiveSession();
         }
         return GoogleSignIn.getClient(context, GoogleSignInOptions.DEFAULT_SIGN_IN).signOut();

auth/src/main/java/com/firebase/ui/auth/data/remote/TwitterSignInHandler.java

@@ -50,6 +50,14 @@ public TwitterSignInHandler(Application application) {
         mClient = new TwitterAuthClient();
     }
 
+    public static void initializeTwitter() {
+        // This method is intentionally empty, but calling it forces the static {} block of this
+        // class to be executed (if it wasn't already).
+        //
+        // Even though it's currently safe to initialize Twitter more than once, this protects
+        // against a future behavior change and gives a small efficiency gain.
+    }
+
     private static IdpResponse createIdpResponse(
             TwitterSession session, String email, String name, Uri photoUri) {
         return new IdpResponse.Builder(