Adding a SQL implementation of the backing store for previews opt outs

components/previews/core/BUILD.gn

Index: components/previews/core/BUILD.gn
diff --git a/components/previews/core/BUILD.gn b/components/previews/core/BUILD.gn
index ab80cb825ad91a3b7cf56d9f40da3eb6f326842d..a1492ad637d9013c4b4983fde74496e5e112d52f 100644
--- a/components/previews/core/BUILD.gn
+++ b/components/previews/core/BUILD.gn
@@ -8,28 +8,31 @@ static_library("core") {
     "previews_black_list.h",
     "previews_black_list_item.cc",
     "previews_black_list_item.h",
     "previews_data_savings.cc",
     "previews_data_savings.h",
     "previews_experiments.cc",
     "previews_experiments.h",
     "previews_io_data.cc",
     "previews_io_data.h",
     "previews_opt_out_store.h",
+    "previews_opt_out_store_sql.cc",
+    "previews_opt_out_store_sql.h",
     "previews_ui_service.cc",
     "previews_ui_service.h",
   ]
 
   deps = [
     "//base",
     "//components/data_reduction_proxy/core/common",
     "//components/variations",
+    "//sql",
     "//url:url",
   ]
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "previews_black_list_item_unittest.cc",
     "previews_black_list_unittest.cc",
     "previews_data_savings_unittest.cc",