Clean up Smart Lock cryptohome keys logic:

chrome/browser/chromeos/login/easy_unlock/easy_unlock_refresh_keys_operation.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 "base/bind.h"
+#include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_create_keys_operation.h"
+#include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_refresh_keys_operation.h"
+#include "chrome/browser/chromeos/login/easy_unlock/easy_unlock_remove_keys_operation.h"
+
+namespace chromeos {
+
+EasyUnlockRefreshKeysOperation::EasyUnlockRefreshKeysOperation(
+    const UserContext& user_context,
+    const EasyUnlockDeviceKeyDataList& devices,
+    const RefreshKeysCallback& callback)
+    : user_context_(user_context),
+      devices_(devices),
+      callback_(callback),
+      weak_ptr_factory_(this) {
+}
+
+EasyUnlockRefreshKeysOperation::~EasyUnlockRefreshKeysOperation() {
+}
+
+void EasyUnlockRefreshKeysOperation::Start() {
+  if (devices_.empty()) {
+    OnKeysCreated(true);
+    return;
+  }
+
+  create_keys_operation_.reset(new EasyUnlockCreateKeysOperation(
+      user_context_, devices_,
+      base::Bind(&EasyUnlockRefreshKeysOperation::OnKeysCreated,
+                 weak_ptr_factory_.GetWeakPtr())));
+  create_keys_operation_->Start();
+}
+
+void EasyUnlockRefreshKeysOperation::OnKeysCreated(bool success) {
+  if (!success) {
+    callback_.Run(false);
+    return;
+  }
+
+  remove_keys_operation_.reset(new EasyUnlockRemoveKeysOperation(
+      user_context_, devices_.size(),

[xiyuan, 2014/12/17 00:23:14]

Think we need to follow existing code to use the user_context() from the create
operation. This is needed when the phone key inside user_context_ is changed
during the create operation. Once create operation finishes, cryptohome would no
longer accept the old phone key and we have to switch to use the just created
key.

[Tim Song, 2014/12/17 02:05:14]

Hmm... I tested this and easy sign-in still works across multiple sessions. The
create keys operation doesn't destroy the old key, so it should still be valid
to use for the delete keys operation, right?

I'm not super familiar with the cryptauth code, so if you think this is
necessary, I'll change it.

[xiyuan, 2014/12/17 03:26:33]

This works now because we have one and only one key and RemoveKey op is actually
a no-op. Create key operation destroy the old key. After it returns, the old key
is no longer accepted by cryptohome. And RemoveKey would end up with
CRYPTOHOME_ERROR_AUTHORIZATION_KEY_NOT_FOUND instead of
CRYPTOHOME_ERROR_KEY_NOT_FOUND.  You can verify that in kernel log as well. 

[Tim Song, 2014/12/17 20:57:57]

Done.

+      base::Bind(&EasyUnlockRefreshKeysOperation::OnKeysRemoved,
+                 weak_ptr_factory_.GetWeakPtr())));
+  remove_keys_operation_->Start();
+}
+
+void EasyUnlockRefreshKeysOperation::OnKeysRemoved(bool success) {
+  callback_.Run(success);
+}
+
+}  // namespace chromeos