Save and Recall: Add unittest for DeskModelWrapper

This CL adds unittests for DeskModelWrapper. It also fixes a bug for
finding an admin template uuid that was found during unit testing.

BUG=1323946
TEST= DeskModelWrapperTest*

Change-Id: I40310a062f69bc293121cdfaba0dcb59fbaeccfb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3643038
Commit-Queue: Matthew Zhu <zhumatthew@google.com>
Reviewed-by: Yanzhu Du <yzd@google.com>
Cr-Commit-Position: refs/heads/main@{#1002402}

components/desks_storage/BUILD.gn

@@ -44,6 +44,7 @@ static_library("desks_storage") {
 source_set("unit_tests") {
   testonly = true
   sources = [
+    "core/desk_model_wrapper_unittests.cc",
     "core/desk_sync_bridge_unittest.cc",
     "core/desk_template_conversion_unittests.cc",
     "core/desk_template_util_unittests.cc",

components/desks_storage/core/desk_model_wrapper.cc

@@ -42,6 +42,15 @@ void DeskModelWrapper::GetAllEntries(
 void DeskModelWrapper::GetEntryByUUID(
     const std::string& uuid,
     DeskModel::GetEntryByUuidCallback callback) {
+  // Check if this is an admin template uuid first.
+  std::unique_ptr<ash::DeskTemplate> policy_entry =
+      GetAdminDeskTemplateByUUID(uuid);
+
+  if (policy_entry) {
+    std::move(callback).Run(GetEntryByUuidStatus::kOk, std::move(policy_entry));
+    return;
+  }
+
   if (GetDeskTemplateModel()->HasUuid(uuid)) {
     GetDeskTemplateModel()->GetEntryByUUID(uuid, std::move(callback));
   } else {