Add missing include guards

R=ahaas@chromium.org

Change-Id: Ie46dce0e417ce528bbd81aa6ef87ca63a9fcc869
Reviewed-on: https://chromium-review.googlesource.com/593613Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47005}

src/base/template-utils.h

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#ifndef V8_BASE_TEMPLATE_UTILS_H
+#define V8_BASE_TEMPLATE_UTILS_H
+
 #include <array>
 #include <memory>
 
@@ -54,3 +57,5 @@ std::unique_ptr<T> make_unique(Args&&... args) {
 
 }  // namespace base
 }  // namespace v8
+
+#endif  // V8_BASE_TEMPLATE_UTILS_H