Fix failing NavigationManagerUtil test that wasn't being run.

ios/web/test/fakes/BUILD.gn

Index: ios/web/test/fakes/BUILD.gn
diff --git a/ios/web/test/fakes/BUILD.gn b/ios/web/test/fakes/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..8e70d783214286d5afe5321a6de1f9dd547632e0
--- /dev/null
+++ b/ios/web/test/fakes/BUILD.gn
@@ -0,0 +1,17 @@
+# 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("fakes") {
+  configs += [ "//build/config/compiler:enable_arc" ]
+  testonly = true
+
+  deps = [
+    "//ios/web:web",
+  ]
+
+  sources = [
+    "test_navigation_manager_delegate.h",
+    "test_navigation_manager_delegate.mm",
+  ]
+}