Query API: Introduces an OfflinePageModelQuery object.

components/offline_pages/BUILD.gn

Index: components/offline_pages/BUILD.gn
diff --git a/components/offline_pages/BUILD.gn b/components/offline_pages/BUILD.gn
index 136503ecd0eb872d47e9aedc7e573f6fcba879ac..0b12ffb8ba86634f9bb9cfef3cf68bf243d50ceb 100644
--- a/components/offline_pages/BUILD.gn
+++ b/components/offline_pages/BUILD.gn
@@ -30,6 +30,8 @@ static_library("offline_pages") {
     "offline_page_model_event_logger.h",
     "offline_page_model_impl.cc",
     "offline_page_model_impl.h",
+    "offline_page_model_query.cc",
+    "offline_page_model_query.h",
     "offline_page_storage_manager.cc",
     "offline_page_storage_manager.h",
     "offline_page_types.h",
@@ -89,6 +91,7 @@ source_set("unit_tests") {
     "offline_page_metadata_store_impl_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",
   ]