Re-add OfflinePageModelQueryTests to build files.

It got lost in https://codereview.chromium.org/2489443002/
(see changes to components/offline_pages/BUILD.gn and
components/offline_pages/core/BUILD.gn in that change).

BUG=654635,661774

Review-Url: https://codereview.chromium.org/2849513003
Cr-Commit-Position: refs/heads/master@{#467792}

components/offline_pages/core/BUILD.gn

@@ -97,6 +97,7 @@ source_set("unit_tests") {
     "offline_page_metadata_store_unittest.cc",
     "offline_page_model_event_logger_unittest.cc",
     "offline_page_model_impl_unittest.cc",
+    "offline_page_model_query_unittest.cc",
     "offline_page_storage_manager_unittest.cc",
     "snapshot_controller_unittest.cc",
     "task_queue_unittest.cc",

components/offline_pages/core/offline_page_model_query_unittest.cc

@@ -2,13 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/time/time.h"
-#include "components/offline_pages/client_namespace_constants.h"
-#include "components/offline_pages/client_policy_controller.h"
 #include "components/offline_pages/core/offline_page_model_query.h"
-#include "components/offline_pages/offline_page_client_policy.h"
-#include "components/offline_pages/offline_page_item.h"
 
+#include "base/time/time.h"
+#include "components/offline_pages/core/client_namespace_constants.h"
+#include "components/offline_pages/core/client_policy_controller.h"
+#include "components/offline_pages/core/offline_page_client_policy.h"
+#include "components/offline_pages/core/offline_page_item.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace offline_pages {