Move ScopedIPCSupport into its own build rule.

ipc/mojo/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/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 
 mojom("mojom") {
   sources = [
     "ipc.mojom",
   ]
 }
 
 component("mojo") {
   sources = [
     "ipc_channel_mojo.cc",
     "ipc_channel_mojo.h",
     "ipc_message_pipe_reader.cc",
     "ipc_message_pipe_reader.h",
     "ipc_mojo_bootstrap.cc",
     "ipc_mojo_bootstrap.h",
     "ipc_mojo_handle_attachment.cc",
     "ipc_mojo_handle_attachment.h",
     "ipc_mojo_message_helper.cc",
     "ipc_mojo_message_helper.h",
     "ipc_mojo_param_traits.cc",
     "ipc_mojo_param_traits.h",
-    "scoped_ipc_support.cc",
-    "scoped_ipc_support.h",
   ]
 
   defines = [ "IPC_MOJO_IMPLEMENTATION" ]
 
   deps = [
     ":mojom",
     "//base",
     "//base/third_party/dynamic_annotations",
     "//ipc",
+    "//mojo/public/c/system",
+    "//mojo/public/cpp/bindings",
+  ]
+}
+
+source_set("ipc_support") {
+  sources = [
+    "scoped_ipc_support.cc",
+    "scoped_ipc_support.h",
+  ]
+
+  deps = [
+    "//base",
     "//mojo/edk/system",
-    "//mojo/public/cpp/bindings",
   ]
 }
 
 test("ipc_mojo_unittests") {
   sources = [
     "ipc_channel_mojo_unittest.cc",
     "ipc_mojo_bootstrap_unittest.cc",
     "run_all_unittests.cc",
   ]
 
@@ skipping 29 matching lines @@
     "//mojo/edk/system",
     "//mojo/edk/test:test_support",
     "//mojo/edk/test:test_support_impl",
     "//url",
   ]
 
   if (is_linux && !is_component_build) {
     public_configs = [ "//build/config/gcc:rpath_for_built_shared_libraries" ]
   }
 }