Add GenericSharedMemoryId and use w/ GpuMemoryBuffer

content/common/generic_shared_memory_id_generator.cc

+// Copyright 2015 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.
+
+#include "content/common/generic_shared_memory_id_generator.h"
+
+#include "base/atomic_sequence_num.h"
+
+namespace content {
+namespace {
+
+// Global atomic to generate gpu memory buffer unique IDs.
+base::StaticAtomicSequenceNumber g_next_generic_shared_memory_id;
+
+}  // namespace
+
+gfx::GenericSharedMemoryId GetNextGenericSharedMemoryId() {
+  return gfx::GenericSharedMemoryId(g_next_generic_shared_memory_id.GetNext());
+}
+
+}  // namespace content