Issue 463: Provide a signout\logout method

Src/GoogleApis.Auth.WinRT/OAuth2/AuthorizationCodeWinRTInstalledApp.cs

Index: Src/GoogleApis.Auth.WinRT/OAuth2/AuthorizationCodeWinRTInstalledApp.cs
===================================================================
--- a/Src/GoogleApis.Auth.WinRT/OAuth2/AuthorizationCodeWinRTInstalledApp.cs
 b/Src/GoogleApis.Auth.WinRT/OAuth2/AuthorizationCodeWinRTInstalledApp.cs
@@ -31,15 31,25 @@
 /// </summary>
 public sealed class AuthorizationCodeWinRTInstalledApp : IAuthorizationCodeInstalledApp
 {
- private IAuthorizationCodeInstalledApp innerInstallApp;
 private readonly IAuthorizationCodeInstalledApp innerInstallApp;
- private readonly AuthorizationCodeFlow.Initializer authorizationCodeFlowInitializer;
-
- /// <summary>Constructs a new authorization code installed application for Windows Store.</summary>
- /// <param name="authorizationCodeFlowInitializer">A authorization code flow initializer</param>
 /// <summary>
 /// Constructs a new authorization code for Windows Store application targeting an installed application flow.
 /// </summary>
 /// <param name="authorizationCodeFlowInitializer">An authorization code flow initializer.</param>
 public AuthorizationCodeWinRTInstalledApp(AuthorizationCodeFlow.Initializer authorizationCodeFlowInitializer)
 {
- this.authorizationCodeFlowInitializer = authorizationCodeFlowInitializer;
 innerInstallApp = new AuthorizationCodeInstalledApp(
 new AuthorizationCodeFlow(authorizationCodeFlowInitializer), new AuthorizationCodeBroker());
 }
 /// <summary>
 /// Constructs a new authorization code for Windows Store application targeting an installed application flow.
 /// </summary>
 /// <param name="flow">An authorization code flow.</param>
 public AuthorizationCodeWinRTInstalledApp(IAuthorizationCodeFlow flow)
 {
 innerInstallApp = new AuthorizationCodeInstalledApp(flow, new AuthorizationCodeBroker());
 }
 #region IAuthorizationCodeInstalledApp Members
@@ -56,12 66,6 @@
 public async Task<UserCredential> AuthorizeAsync(string userId, CancellationToken taskCancellationToken)
 {
- if (innerInstallApp == null)
- {
- innerInstallApp = new AuthorizationCodeInstalledApp(
- new AuthorizationCodeFlow(authorizationCodeFlowInitializer), new AuthorizationCodeBroker());
- }
-
 return await innerInstallApp.AuthorizeAsync(userId, taskCancellationToken).ConfigureAwait(false);
 }