[Reland] Mojo: Eliminate duplicate C API symbols

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("//build/config/nacl/config.gni")
 
 source_set("headers") {
   sources = [
     "configuration.h",
     "embedder.h",
@@ skipping 19 matching lines @@
     "//mojo/edk/system",
     "//components/nacl:nacl",
   ]
 
   sources = [
     "configuration.h",
     "embedder.cc",
     "embedder.h",
     "embedder_internal.h",
     "entrypoints.cc",
+    "entrypoints.h",
 
     # 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_IMPL_IMPLEMENTATION",
-    "MOJO_SYSTEM_IMPLEMENTATION",
-  ]
-
-  configs += [ "//mojo/edk/system:system_config" ]
+  defines = [ "MOJO_SYSTEM_IMPL_IMPLEMENTATION" ]
 
   public_deps = [
     ":delegates",
     ":headers",
     ":platform",
     "//base",
     "//mojo/public/cpp/system",
   ]
 
   if (!is_nacl) {
@@ skipping 26 matching lines @@
     "platform_handle_utils_posix.cc",
     "platform_handle_utils_win.cc",
     "platform_handle_vector.h",
     "platform_shared_buffer.cc",
     "platform_shared_buffer.h",
     "scoped_platform_handle.h",
   ]
 
   defines = [ "MOJO_SYSTEM_IMPL_IMPLEMENTATION" ]
 
-  configs += [ "//mojo/edk/system:system_config" ]
-
   public_deps = [
     "//mojo/public/cpp/system",
   ]
 
   deps = [
     "//base",
   ]
 
   if (is_android) {
     deps += [ "//third_party/ashmem" ]
@@ skipping 11 matching lines @@
     ":embedder",
     "//mojo/edk/system",
   ]
 
   sources = [
     "process_delegate.h",
   ]
 
   defines = [ "MOJO_SYSTEM_IMPL_IMPLEMENTATION" ]
 
-  configs += [ "//mojo/edk/system:system_config" ]
-
   public_deps = [
     "//mojo/public/cpp/system",
   ]
 }
 
 source_set("embedder_unittests") {
   testonly = true
 
   # TODO: Figure out why this visibility check fails on Android.
   # visibility = [ "//mojo/edk/system:mojo_system_unittests" ]
 
   sources = [
     "embedder_unittest.cc",
     "platform_channel_pair_posix_unittest.cc",
     "platform_shared_buffer_unittest.cc",
   ]
 
   deps = [
     "//base",
     "//base/test:test_support",
     "//mojo/edk/system",
     "//mojo/edk/system:test_utils",
     "//mojo/edk/test:test_support",
     "//testing/gtest",
   ]
 }