Revert of delete the levelDB storage implementation.

components/offline_pages/proto/BUILD.gn

Index: components/offline_pages/proto/BUILD.gn
diff --git a/components/offline_pages/proto/BUILD.gn b/components/offline_pages/proto/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..7cfb1a6f4740b8de31457a07d90e56798c475ce3
--- /dev/null
+++ b/components/offline_pages/proto/BUILD.gn
@@ -0,0 +1,12 @@
+# Copyright 2015 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//third_party/protobuf/proto_library.gni")
+
+# GYP version: components/offline_pages.gypi:offline_pages_proto
+proto_library("offline_pages_proto") {
+  sources = [
+    "offline_pages.proto",
+  ]
+}