Create an Obj-C bridge for MostVisitedSitesObserver

components/ntp_tiles/ios/BUILD.gn

Index: components/ntp_tiles/ios/BUILD.gn
diff --git a/components/ntp_tiles/ios/BUILD.gn b/components/ntp_tiles/ios/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..dacacb8f6346123453ff1f8c71c9a697e233869a
--- /dev/null
+++ b/components/ntp_tiles/ios/BUILD.gn
@@ -0,0 +1,14 @@
+# Copyright 2017 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.
+
+source_set("ios") {
+  sources = [
+    "most_visited_sites_bridge_observer.h",
+    "most_visited_sites_bridge_observer.mm",
+  ]
+  deps = [
+    "//components/ntp_tiles",
+  ]
+  configs += [ "//build/config/compiler:enable_arc" ]
+}