[LayoutNG] remove obsolete ng_macros.h

Bug: 635619
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: I2fd589b4db0fbeba4b142d130fb95f9cb804bc49
Reviewed-on: https://chromium-review.googlesource.com/889681Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Commit-Queue: Aleks Totic <atotic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532266}

third_party/WebKit/Source/core/layout/BUILD.gn

@@ -429,7 +429,6 @@ blink_core_sources("layout") {
     "ng/ng_layout_result.h",
     "ng/ng_length_utils.cc",
     "ng/ng_length_utils.h",
-    "ng/ng_macros.h",
     "ng/ng_out_of_flow_layout_part.cc",
     "ng/ng_out_of_flow_layout_part.h",
     "ng/ng_out_of_flow_positioned_descendant.h",

third_party/WebKit/Source/core/layout/ng/ng_macros.h

-// Copyright 2016 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.
-
-#ifndef ng_macros_h
-#define ng_macros_h
-
-#include "base/macros.h"
-
-namespace blink {
-
-// Macro that can be used to annotate cases where it's OK to ignore writing
-// mode. This is because changing the writing mode establishes a new formatting
-// context and can be ignored while accessing some properties that are only
-// stored in physical constraint space. Example: MarginStrut.
-#ifndef WRITING_MODE_IGNORED
-#define WRITING_MODE_IGNORED(message)
-#endif
-
-}  // namespace blink
-
-#endif  // ng_macros_h