Add a throttle wrapper to OfflineContentProvider

components/offline_items_collection/core/BUILD.gn

Index: components/offline_items_collection/core/BUILD.gn
diff --git a/components/offline_items_collection/core/BUILD.gn b/components/offline_items_collection/core/BUILD.gn
index 5b910afe6c4d62e475b957e1fa429c31c75e9166..98c42545fcf163ccc5fb3d72ce6d6a7ceedc4fe4 100644
--- a/components/offline_items_collection/core/BUILD.gn
+++ b/components/offline_items_collection/core/BUILD.gn
@@ -16,6 +16,8 @@ static_library("core") {
     "offline_item.h",
     "offline_item_filter.h",
     "offline_item_state.h",
+    "throttled_offline_content_provider.cc",
+    "throttled_offline_content_provider.h",
   ]
 
   public_deps = [
@@ -43,6 +45,7 @@ source_set("unit_tests") {
 
   sources = [
     "offline_content_aggregator_unittest.cc",
+    "throttled_offline_content_provider_unittest.cc",
   ]
 
   deps = [