Adding a BUILD file for both gyp and gn for the new background_offlining

components/offline_pages/background/BUILD.gn

Index: components/offline_pages/background/BUILD.gn
diff --git a/components/offline_pages/background/BUILD.gn b/components/offline_pages/background/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..96448fd4068ecc6ed8b0ce88d550d9bb81e75f55
--- /dev/null
+++ b/components/offline_pages/background/BUILD.gn
@@ -0,0 +1,22 @@
+# Copyright 2016 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.
+
+if (is_android) {
+  import("//build/config/android/rules.gni")
+}
+
+# GYP: //components/offline_pages/offline_pages.gypi:background_offlining
+static_library("background_offlining") {
+  sources = [
+    "request_coordinator.cc",
+  ]
+
+  deps = [
+    "//base",
+    "//components/bookmarks/browser",
+    "//components/offline_pages:offline_pages",
+    "//net",
+    "//url",
+  ]
+}