Add SyncAuthProvider interface and implementation

chrome/browser/sync/profile_sync_auth_provider.cc

+// Copyright 2014 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.
+
+#include "chrome/browser/sync/profile_sync_auth_provider.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/message_loop/message_loop_proxy.h"
+#include "base/single_thread_task_runner.h"
+#include "components/signin/core/browser/profile_oauth2_token_service.h"
+#include "google_apis/gaia/gaia_constants.h"
+
+// This is thin proxy class for forwarding calls between sync and UI threads.
+// The main purpose is to hide the fact that ProfileSyncAuthProvider and
+// SyncThreadProxy have independent lifetimes. If ProfileSyncAuthProvider is
+// destroyed first calls to RequestAccessToken will never complete. This is fine
+// since sync thread is not blocked and is in the process of shutdown anyway.
+class ProfileSyncAuthProvider::SyncThreadProxy
+    : public syncer::SyncAuthProvider,
+      public base::NonThreadSafe {
+ public:
+  SyncThreadProxy(
+      base::WeakPtr<ProfileSyncAuthProvider> provider_impl,
+      scoped_refptr<base::SingleThreadTaskRunner> provider_task_runner);
+
+  // syncer::SyncAuthProvider implementation.
+  virtual void RequestAccessToken(
+      const RequestTokenCallback& callback) OVERRIDE;
+  virtual void InvalidateAccessToken(const std::string& token) OVERRIDE;
+
+ private:
+  base::WeakPtr<ProfileSyncAuthProvider> provider_impl_;
+  scoped_refptr<base::SingleThreadTaskRunner> provider_task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(SyncThreadProxy);
+};
+
+ProfileSyncAuthProvider::SyncThreadProxy::SyncThreadProxy(
+    base::WeakPtr<ProfileSyncAuthProvider> provider_impl,
+    scoped_refptr<base::SingleThreadTaskRunner> provider_task_runner)
+    : provider_impl_(provider_impl),
+      provider_task_runner_(provider_task_runner) {
+  // SyncThreadProxy is created on UI thread but used on sync thread.
+  // Detach NonThreadSafe from UI thread so that it can reattach on first

[tim (not reviewing), 2014/04/30 20:52:41]

finish sentence.

[pavely, 2014/04/30 21:16:56]

Done.

+  DetachFromThread();
+}
+
+void ProfileSyncAuthProvider::SyncThreadProxy::RequestAccessToken(
+    const RequestTokenCallback& callback) {
+  DCHECK(CalledOnValidThread());
+  provider_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&ProfileSyncAuthProvider::RequestAccessToken,
+                 provider_impl_,
+                 callback,
+                 base::MessageLoopProxy::current()));
+}
+
+void ProfileSyncAuthProvider::SyncThreadProxy::InvalidateAccessToken(
+    const std::string& token) {
+  DCHECK(CalledOnValidThread());
+  provider_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&ProfileSyncAuthProvider::InvalidateAccessToken,
+                 provider_impl_,
+                 token));
+}
+
+ProfileSyncAuthProvider::ProfileSyncAuthProvider(
+    ProfileOAuth2TokenService* token_service,
+    const std::string& account_id,
+    const std::string& scope)
+    : OAuth2TokenService::Consumer("sync_auth_provider"),
+      token_service_(token_service),
+      account_id_(account_id),
+      weak_factory_(this) {
+  oauth2_scope_.insert(scope);
+}
+
+ProfileSyncAuthProvider::~ProfileSyncAuthProvider() {
+  DCHECK(CalledOnValidThread());
+}
+
+void ProfileSyncAuthProvider::RequestAccessToken(
+    const syncer::SyncAuthProvider::RequestTokenCallback& callback,
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
+  DCHECK(CalledOnValidThread());
+  if (access_token_request_ != NULL) {
+    // If there is already pending request report it as cancelled.
+    GoogleServiceAuthError error(GoogleServiceAuthError::REQUEST_CANCELED);
+    RespondToTokenRequest(error, std::string());
+  }
+  request_token_callback_ = callback;
+  callback_task_runner_ = task_runner;
+  access_token_request_ =
+      token_service_->StartRequest(account_id_, oauth2_scope_, this);
+}
+
+void ProfileSyncAuthProvider::OnGetTokenSuccess(
+    const OAuth2TokenService::Request* request,
+    const std::string& access_token,
+    const base::Time& expiration_time) {
+  DCHECK_EQ(access_token_request_, request);
+  RespondToTokenRequest(GoogleServiceAuthError::AuthErrorNone(), access_token);
+}
+
+void ProfileSyncAuthProvider::OnGetTokenFailure(
+    const OAuth2TokenService::Request* request,
+    const GoogleServiceAuthError& error) {
+  DCHECK_EQ(access_token_request_, request);
+  RespondToTokenRequest(error, std::string());
+}
+
+void ProfileSyncAuthProvider::RespondToTokenRequest(
+    const GoogleServiceAuthError& error,
+    const std::string& token) {
+  DCHECK(CalledOnValidThread());
+  callback_task_runner_->PostTask(

[tim (not reviewing), 2014/04/30 20:52:41]

It's possible this response hits the client (SCM) after the client issues a
subsequent call to SyncThreadProxy::RequestAccessToken. Which means the client
will later get the response for the subsequent call with neither having been
explicitly cancelled by PSAP.

Is that correct? If so, do we need to bother returning REQUEST_CANCELLED at all
above?

[pavely, 2014/04/30 21:16:56]

The model I'm trying to follow is: For each RequestToken call there will be
exactly one callback invocation. The reason is the same, easier to reason about
what can or cannot happen in consumer code.

PSAP only keeps reference to last token request. If first request didn't finish
then starting second request will reset access_token_request_ and therefore no
callback from OAuth2TokenService will be called with regards to first request.
Responding with REQUEST_CANCELLED in this case is the way to follow above model.

+      FROM_HERE, base::Bind(request_token_callback_, error, token));
+  access_token_request_.reset();
+  request_token_callback_.Reset();
+  callback_task_runner_ = NULL;
+}
+
+void ProfileSyncAuthProvider::InvalidateAccessToken(const std::string& token) {
+  DCHECK(CalledOnValidThread());
+  token_service_->InvalidateToken(account_id_, oauth2_scope_, token);
+}
+
+scoped_ptr<syncer::SyncAuthProvider>
+ProfileSyncAuthProvider::CreateProviderForSyncThread() {
+  DCHECK(CalledOnValidThread());
+  scoped_ptr<syncer::SyncAuthProvider> auth_provider(new SyncThreadProxy(
+      weak_factory_.GetWeakPtr(), base::MessageLoopProxy::current()));
+  return auth_provider.Pass();
+}