Blimp OAuth2 token retreival on application start up.

blimp/client/core/session/identity_source.h

Index: blimp/client/core/session/identity_source.h
diff --git a/blimp/client/core/session/identity_source.h b/blimp/client/core/session/identity_source.h
new file mode 100644
index 0000000000000000000000000000000000000000..138ff1e2455da289252228caa95fd70740ec5625
--- /dev/null
+++ b/blimp/client/core/session/identity_source.h
@@ -0,0 +1,75 @@
+// Copyright 2016 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.
+
+#ifndef BLIMP_CLIENT_CORE_SESSION_IDENTITY_SOURCE_H_
+#define BLIMP_CLIENT_CORE_SESSION_IDENTITY_SOURCE_H_
+
+#include <memory>
+#include <string>
+
+#include "base/callback.h"
+#include "base/macros.h"
+
+#include "blimp/client/public/blimp_client_context_delegate.h"
+#include "google_apis/gaia/identity_provider.h"
+#include "google_apis/gaia/oauth2_token_service.h"
+
+namespace blimp {
+namespace client {
+
+// IdentitySource handles OAuth2 token request and forward user sign in state
+// change to Blimp with ProfileIdentityProvider.
+class IdentitySource : public OAuth2TokenService::Consumer,
+                       public OAuth2TokenService::Observer,
+                       public IdentityProvider::Observer {
+ public:
+  typedef base::Callback<void(const std::string&)> TokenCallback;
+
+  explicit IdentitySource(std::unique_ptr<IdentityProvider> identity_provider);
+  ~IdentitySource() override;
+
+  // Start Blimp authentication by requesting OAuth2 token from Google.

[nyquist, 2016/08/16 18:38:05]

What happens if I call Connect() multiple times? Possibly with different
callbacks?

[xingliu, 2016/08/17 00:32:24]

This is a good point. Added a bool to filter duplicate connect attempts.

+  void Connect(const TokenCallback& token_callback);
+
+  // Set the BlimpClientContextDelegate object, used to inform states change
+  // to the embedder.
+  void SetDelegate(BlimpClientContextDelegate* delegate);
+
+  // OAuth2TokenService::Consumer implementation.
+  void OnGetTokenSuccess(const OAuth2TokenService::Request* request,
+                         const std::string& access_token,
+                         const base::Time& expiration_time) override;
+  void OnGetTokenFailure(const OAuth2TokenService::Request* request,
+                         const GoogleServiceAuthError& error) override;
+
+  // OAuth2TokenService::Observer implementation.
+  void OnRefreshTokenAvailable(const std::string& account_id) override;
+
+ private:
+  // Fetch OAuth token.
+  void FetchAuthToken();
+
+  // Provide OAuth2 token service and listen to Google account sign in state.
+  std::unique_ptr<IdentityProvider> identity_provider_;
+
+  // OAuth2 token request. The request is created when we start to fetch the
+  // access token in OAuth2TokenService::StartRequest, and destroyed when
+  // OAuth2TokenService::Consumer callback get called.
+  std::unique_ptr<OAuth2TokenService::Request> token_request_;
+
+  // Callback to BlimpClientContextImpl after OAuth2 token is fetched.

[nyquist, 2016/08/16 18:38:06]

I don't think you need to mention BlimpClientContextImpl here, as this class is
able to stand on its own :-)

[xingliu, 2016/08/17 00:32:24]

Done.

+  TokenCallback token_callback_;
+
+  // Account id of current active user, used during token request.
+  std::string account_id_;
+
+  BlimpClientContextDelegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(IdentitySource);
+};
+
+}  // namespace client
+}  // namespace blimp
+
+#endif  // BLIMP_CLIENT_CORE_SESSION_IDENTITY_SOURCE_H_