Allow embedder to use custom cryptography in Autofill table.

components/autofill/core/browser/webdata/autofill_table_encryptor_factory.h

+// Copyright (c) 2017 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 COMPONENTS_WEBDATA_SERVICES_AUTOFILL_TABLE_ENCRYPTOR_FACTORY_H_
+#define COMPONENTS_WEBDATA_SERVICES_AUTOFILL_TABLE_ENCRYPTOR_FACTORY_H_
+
+#include <memory>
+
+#include "base/memory/singleton.h"
+#include "components/autofill/core/browser/webdata/autofill_table_encryptor.h"

[Roger McFarlane (Chromium), 2017/02/17 21:04:08]

nit: forward declare AutofillTaableEncryptor in namespace autofill instead of
including its header.

[devarajn, 2017/02/17 22:28:54]

Done.

[Roger McFarlane (Chromium), 2017/02/22 19:29:50]

I think you forgot this one. It's not done.  :)

[devarajn, 2017/02/22 22:07:59]

Sorry missed it. I will ensure new revision has it.

+
+namespace autofill {
+// Factory for creating Autofill table encryptor.
+// If |delegate_| is set, then |delegate_| is used to create encryptor,
+// else default encrytor (SystemEncryptor) is returned.
+template <typename T>
+struct DefaultSingletonTraits;
+class AutofillTableEncryptorFactory {

[Roger McFarlane (Chromium), 2017/02/17 21:04:09]

What are the expected threading constraints on the factory as well as on the
encryptor? Maybe add a base::SequenceChecker to the factory to assert that the
factory and encryptor are always called from the same sequence.

[devarajn, 2017/02/17 22:28:54]

Make sense! done.

[devarajn, 2017/02/17 23:02:50]

On second thought, can you explain little bit more here.
My take on this is that checking whether calling factory or encryptor on current
thread, shouldn't this be in consumer's contract?
Please help me understand.

Thank you

[Roger McFarlane (Chromium), 2017/02/21 20:57:05]

Create() and SetDelegate() are not threadsafe. This is fine if they are always
called from the same sequence/thread, which can be checked with a
SequenceChecker. The factor is a singleton, so all consumers must adhere to the
same instance of this contract. 

[devarajn, 2017/02/21 21:19:54]

Acknowledged.

+ public:
+  // Embedders are recommended to use this delegate to inject
+  // their encryptor into Autofill table.
+  class Delegate {
+   public:
+    virtual std::unique_ptr<autofill::AutofillTableEncryptor> Create();

[Roger McFarlane (Chromium), 2017/02/17 21:04:08]

nit: no need for autofill::

[devarajn, 2017/02/17 22:28:54]

Done.

+  };
+
+  static AutofillTableEncryptorFactory* GetInstance();
+
+  std::unique_ptr<AutofillTableEncryptor> Create();
+
+  void SetDelegate(
+      std::unique_ptr<autofill::AutofillTableEncryptorFactory::Delegate>

[Roger McFarlane (Chromium), 2017/02/17 21:04:08]

nit: no need for autofill::AutofillEncryptorFactory::

here and below

[devarajn, 2017/02/17 22:28:54]

Done.

+          delegate);
+
+ private:
+  AutofillTableEncryptorFactory();
+  std::unique_ptr<autofill::AutofillTableEncryptorFactory::Delegate> delegate_;
+
+  friend struct base::DefaultSingletonTraits<AutofillTableEncryptorFactory>;
+  DISALLOW_COPY_AND_ASSIGN(AutofillTableEncryptorFactory);
+};
+
+}  // namespace autofill
+
+#endif  // COMPONENTS_WEBDATA_SERVICES_AUTOFILL_TABLE_ENCRYPTOR_FACTORY_H_