Get rid of system_export.h, etc.

mojo/edk/embedder/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_edk.gni")
 
 mojo_edk_source_set("embedder") {
   # This isn't really a standalone target; it must be linked into the
   # mojo_system_impl component.
   mojo_edk_visibility = [ "mojo/edk/system" ]
 
   sources = [
     "channel_info_forward.h",
     "configuration.h",
     "embedder.cc",
     "embedder.h",
     "embedder_internal.h",
     "entrypoints.cc",
     "system_impl_private_entrypoints.cc",
 
     # Test-only code:
     # TODO(vtl): It's a little unfortunate that these end up in the same
     # component as non-test-only code. In the static build, this code should
     # hopefully be dead-stripped.
     "test_embedder.cc",
     "test_embedder.h",
   ]
 
-  defines = [ "MOJO_SYSTEM_IMPLEMENTATION" ]
-
   mojo_edk_configs = [ "mojo/edk/system:system_config" ]
 
   public_deps = [
     ":delegates",
     ":platform",
   ]
 
   mojo_sdk_deps = [ "mojo/public/platform/native:system_impl_private_api" ]
 
   mojo_sdk_public_deps = [ "mojo/public/cpp/system" ]
@@ skipping 91 matching lines @@
     "//testing/gtest",
   ]
 
   mojo_edk_deps = [
     "mojo/edk/test:test_support",
     "mojo/edk/system",
     "mojo/edk/system:test_utils",
     "mojo/edk/util",
   ]
 }