Change the canonical way to include the C macros.h to <mojo/macros.h>.

mojo/edk/platform/BUILD.gn

 # Copyright 2015 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")
 
 # Declares/defines platform-dependent things. Some things are left
 # unimplemented, and the final binary must include a separate implementation
 # (e.g., //mojo/edk/base_edk, which implements these platform-dependent things
 # using //base).
@@ skipping 11 matching lines @@
     "platform_shared_buffer.h",
     "random.h",
     "scoped_platform_handle.h",
     "simple_platform_shared_buffer.h",
     "task_runner.h",
     "thread.h",
     "thread_utils.h",
     "time_ticks.h",
   ]
 
-  mojo_sdk_public_deps = [ "mojo/public/cpp/system" ]
+  mojo_sdk_public_deps = [
+    "mojo/public/c:system",
+    "mojo/public/cpp/system",
+  ]
 
   mojo_edk_public_deps = [ "mojo/edk/util" ]
 }
 
 # Functionality to be used by tests (both those merely using :platform as well
 # as those implementing the unimplemented parts of :platform).
 mojo_edk_source_set("test_platform") {
   testonly = true
 
   sources = [
@@ skipping 40 matching lines @@
     ":test_platform",
     "//testing/gtest",
   ]
 
   # TODO(vtl): This is a suboptimal dependency, but we have to get timeouts from
   # somewhere.
   mojo_edk_deps = [ "mojo/edk/system/test" ]
 
   mojo_sdk_deps = [ "mojo/public/cpp/system" ]
 }