EDK: Remove MOJO_SYSTEM_IMPL_EXPORT, system_impl_export.h, etc.

mojo/edk/system/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")
 import("//testing/test.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
@@ skipping 96 matching lines @@
     "slave_connection_manager.h",
     "thread_annotations.h",
     "transport_data.cc",
     "transport_data.h",
     "unique_identifier.cc",
     "unique_identifier.h",
     "waiter.cc",
     "waiter.h",
   ]
 
-  defines = [
-    "MOJO_SYSTEM_IMPL_IMPLEMENTATION",
-    "MOJO_SYSTEM_IMPLEMENTATION",
-  ]
+  defines = [ "MOJO_SYSTEM_IMPLEMENTATION" ]
 
   all_dependent_configs = [ ":system_config" ]
 
   public_deps = [
     "../embedder",
     "../embedder:delegates",
     "../embedder:platform",
     "../util",
     "../../public/c/system",
     "../../public/cpp/system",
@@ skipping 107 matching lines @@
   deps = [
     ":system",
     ":test_utils",
     "../test:test_support",
     "//base",
     "//base/test:test_support",
     "//base/test:test_support_perf",
     "//testing/gtest",
   ]
 }