Add a new QUIC platform API quic_aligned.h for the alignment macro definitions.

net/quic/platform/impl/quic_aligned_impl.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 NET_QUIC_PLATFORM_IMPL_QUIC_ALIGNED_IMPL_H_
+#define NET_QUIC_PLATFORM_IMPL_QUIC_ALIGNED_IMPL_H_
+
+#ifdef _MSC_VER
+// MSVC 2013 and prior don't have alignof or aligned(); they have __alignof and
+// a __declspec instead.
+#define QUIC_ALIGN_OF_IMPL __alignof
+#define QUIC_ALIGNED_IMPL(X) __declspec(align(X))
+#else
+#define QUIC_ALIGN_OF_IMPL alignof
+#define QUIC_ALIGNED_IMPL(X) __attribute__((aligned(X)))
+#endif  // _MSC_VER
+
+// TODO(rtenneti): Change the default 64 alignas value (used the default
+// value from CACHELINE_SIZE).
+#define QUIC_CACHELINE_ALIGNED_IMPL ALIGNAS(64)
+
+#endif  // NET_QUIC_PLATFORM_IMPL_QUIC_ALIGNED_IMPL_H_