[DeviceSync v2] Fix CryptAuthDeviceSyncResult equality operator

Add a comparison for did_device_registry_change_.

Also, simplified the function by extracting the ClientDirective
comparison and simplifying that logic.

Bug: 951969
Change-Id: I61809ed953e711502c3a058c51cc1315888e8e20
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1747376
Commit-Queue: Josh Nohle <nohle@chromium.org>
Auto-Submit: Josh Nohle <nohle@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#686097}

chromeos/services/device_sync/cryptauth_device_sync_result.cc

@@ -45,11 +45,14 @@ bool CryptAuthDeviceSyncResult::IsSuccess() const {
 
 bool CryptAuthDeviceSyncResult::operator==(
     const CryptAuthDeviceSyncResult& other) const {
-  return result_code_ == other.result_code_ &&
-         client_directive_.has_value() == other.client_directive_.has_value() &&
-         (!client_directive_ ||
-          client_directive_->SerializeAsString() ==
-              other.client_directive_->SerializeAsString());
+  bool client_directives_agree =
+      (!client_directive_.has_value() &&
+       !other.client_directive_.has_value()) ||
+      (client_directive_.has_value() && other.client_directive_.has_value() &&
+       client_directive_->SerializeAsString() ==
+           other.client_directive_->SerializeAsString());
+  return client_directives_agree && result_code_ == other.result_code_ &&
+         did_device_registry_change_ == other.did_device_registry_change_;
 }
 
 bool CryptAuthDeviceSyncResult::operator!=(