Upstream ios/showcase source code.

ios/showcase/common/BUILD.gn

Index: ios/showcase/common/BUILD.gn
diff --git a/ios/showcase/common/BUILD.gn b/ios/showcase/common/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..3a469136fe0473c0e81700c77c5961efa6c8394c
--- /dev/null
+++ b/ios/showcase/common/BUILD.gn
@@ -0,0 +1,11 @@
+# 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.
+
+source_set("common") {
+  sources = [
+    "coordinator.h",
+  ]
+  libs = [ "Foundation.framework" ]
+  configs += [ "//build/config/compiler:enable_arc" ]
+}