Use C++11 alignment primitives

components/tracing/core/proto_zero_message.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 COMPONENTS_TRACING_CORE_PROTO_ZERO_MESSAGE_H_
 #define COMPONENTS_TRACING_CORE_PROTO_ZERO_MESSAGE_H_
 
 #include <stdint.h>
 
 #include <type_traits>
@@ skipping 181 matching lines @@
   // nested messages are finalized and sealed when any other field is set in the
   // parent message (or the parent message itself is finalized) and cannot be
   // accessed anymore afterwards.
   ProtoZeroMessage* nested_message_;
 
   // The root message owns the storage for all its nested messages, up to a max
   // of kMaxNestingDepth levels (see the .cc file). Note that the boundaries of
   // the arena are meaningful only for the root message. The static_assert in
   // the .cc file guarantees that the sizeof(nested_messages_arena_) is enough
   // to contain up to kMaxNestingDepth messages.
-  ALIGNAS(sizeof(void*)) uint8_t nested_messages_arena_[512];
+  alignas(sizeof(void*)) uint8_t nested_messages_arena_[512];
 
   // DO NOT add any fields below |nested_messages_arena_|. The memory layout of
   // nested messages would overflow the storage allocated by the root message.
 
   DISALLOW_COPY_AND_ASSIGN(ProtoZeroMessage);
 };
 
 }  // namespace v2
 }  // namespace tracing
 
 #endif  // COMPONENTS_TRACING_CORE_PROTO_ZERO_MESSAGE_H_