diff -up chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/DEPS.944404 chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/DEPS
--- chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/DEPS.944404	2018-04-23 14:18:43.702116916 -0400
+++ chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/DEPS	2018-04-23 14:19:05.854680223 -0400
@@ -16,6 +16,7 @@ include_rules = [
     "+base/process/process_metrics.h",
     "+base/rand_util.h",
     "+base/strings",
+    "+base/template_util.h",
     "+base/threading/thread_checker.h",
     "+base/time/time.h",
     "+base/tuple.h",
diff -up chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/Optional.h.944404 chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/Optional.h
--- chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/Optional.h.944404	2018-04-23 14:20:05.718499685 -0400
+++ chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/Optional.h	2018-04-23 14:20:18.165253615 -0400
@@ -6,6 +6,7 @@
 #define Optional_h
 
 #include "base/optional.h"
+#include "platform/wtf/TemplateUtil.h"
 
 namespace WTF {
 
diff -up chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/TemplateUtil.h.944404 chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/TemplateUtil.h
--- chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/TemplateUtil.h.944404	2018-04-23 14:20:31.660987877 -0400
+++ chromium-66.0.3359.117/third_party/WebKit/Source/platform/wtf/TemplateUtil.h	2018-04-23 14:21:40.276637297 -0400
@@ -0,0 +1,27 @@
+// Copyright 2018 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 TemplateUtil_h
+#define TemplateUtil_h
+
+#include "base/template_util.h"
+#include "platform/wtf/Vector.h"
+
+namespace base {
+
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ <= 7
+// Workaround for g++7 and earlier family.
+// Due to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80654, without this
+// Optional<WTF::Vector<T>> where T is non-copyable causes a compile error.
+// As we know it is not trivially copy constructible, explicitly declare so.
+//
+// It completes the declaration in base/template_util.h that was provided
+// for std::vector
+template <typename T>
+struct is_trivially_copy_constructible<WTF::Vector<T>> : std::false_type {};
+#endif
+
+}  // namespace base
+
+#endif  // TemplateUtil_h