Revert of delete the levelDB storage implementation.

components/offline_pages.gypi

Index: components/offline_pages.gypi
diff --git a/components/offline_pages.gypi b/components/offline_pages.gypi
index f0cce514a5af5be4f1249976708e73edbadac86c..304b967601d8c3697897976915910d6b9960a602 100644
--- a/components/offline_pages.gypi
+++ b/components/offline_pages.gypi
@@ -16,7 +16,10 @@
         '../net/net.gyp:net',
         '../url/url.gyp:url_lib',
         '../sql/sql.gyp:sql',
+        '../third_party/leveldatabase/leveldatabase.gyp:leveldatabase',
+        'components.gyp:leveldb_proto',
         'keyed_service_core',
+        'offline_pages_proto',
       ],
       'sources': [
         'offline_pages/archive_manager.cc',
@@ -31,6 +34,8 @@
         'offline_pages/offline_page_item.h',
         'offline_pages/offline_page_metadata_store.cc',
         'offline_pages/offline_page_metadata_store.h',
+        'offline_pages/offline_page_metadata_store_impl.cc',
+        'offline_pages/offline_page_metadata_store_impl.h',
         'offline_pages/offline_page_model.cc',
         'offline_pages/offline_page_model.h',
         'offline_pages/offline_page_storage_manager.cc',
@@ -89,6 +94,18 @@
         'offline_pages/offline_page_test_store.cc',
       ],
     },
+    {
+      # Protobuf compiler / generator for the offline page item protocol buffer.
+      # GN version: //components/offline_pages/proto
+      'target_name': 'offline_pages_proto',
+      'type': 'static_library',
+      'sources': [ 'offline_pages/proto/offline_pages.proto', ],
+      'variables': {
+        'proto_in_dir': 'offline_pages/proto',
+        'proto_out_dir': 'components/offline_pages/proto',
+      },
+      'includes': [ '../build/protoc.gypi', ],
+    },
   ],
   'conditions': [
     ['OS == "android"', {