[Draft] try out the idea of adding export macros for C++ bindings.

mojo/public/cpp/bindings/tests/BUILD.gn

 # Copyright 2014 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("../../../mojo_application.gni")
 
 source_set("tests") {
   testonly = true
 
   sources = [
@@ skipping 76 matching lines @@
 source_set("mojo_public_bindings_test_utils") {
   sources = [
     "validation_test_input_parser.cc",
     "validation_test_input_parser.h",
   ]
 
   deps = [
     "//mojo/public/c/system",
   ]
 }
+
+component("tests_component") {
+  testonly = true
+  defines = [ "CONTENT_IMPLEMENTATION" ]
+  deps = [
+     ":tests",
+    "//third_party/mojo/src/mojo/edk/system",
+#    "//mojo/public/interfaces/bindings/tests:test_interfaces",
+#    ":mojo_public_bindings_test_utils",
+#    "//mojo/common",
+#    "//mojo/environment:chromium",
+#    "//mojo/message_pump",
+#    "//mojo/public/cpp/bindings",
+#    "//mojo/public/cpp/bindings:callback",
+#    "//mojo/public/cpp/system",
+#    "//mojo/public/cpp/test_support:test_utils",
+#    "//mojo/public/cpp/utility",
+  ]
+}