Prefetching: Introduce store commands abstractions to be used by tasks.

components/offline_pages/core/prefetch/BUILD.gn

Index: components/offline_pages/core/prefetch/BUILD.gn
diff --git a/components/offline_pages/core/prefetch/BUILD.gn b/components/offline_pages/core/prefetch/BUILD.gn
index 68e0e514719acde24e6c5ff9abbb7673eaa4c477..fc091261da51a915f576d0875b8cdee6f0f82f13 100644
--- a/components/offline_pages/core/prefetch/BUILD.gn
+++ b/components/offline_pages/core/prefetch/BUILD.gn
@@ -22,8 +22,6 @@ static_library("prefetch") {
     "prefetch_gcm_app_handler.cc",
     "prefetch_gcm_app_handler.h",
     "prefetch_gcm_handler.h",
-    "prefetch_in_memory_store.cc",
-    "prefetch_in_memory_store.h",
     "prefetch_item.cc",
     "prefetch_item.h",
     "prefetch_proto_utils.cc",
@@ -33,9 +31,11 @@ static_library("prefetch") {
     "prefetch_service.h",
     "prefetch_service_impl.cc",
     "prefetch_service_impl.h",
-    "prefetch_store.h",
     "prefetch_types.cc",
     "prefetch_types.h",
+    "store/add_urls_store_command.h",
+    "store/cleanup_zombies_store_command.h",
+    "store/prefetch_store_command_factory.h",
     "suggested_articles_observer.cc",
     "suggested_articles_observer.h",
   ]