Separates out accelerator handling in windowmanager

ash/mus/accelerators/accelerator_ids.h

Index: ash/mus/accelerators/accelerator_ids.h
diff --git a/ash/mus/accelerators/accelerator_ids.h b/ash/mus/accelerators/accelerator_ids.h
new file mode 100644
index 0000000000000000000000000000000000000000..7d9465a5dc5ffff0a50758a35e58cb05b1379753
--- /dev/null
+++ b/ash/mus/accelerators/accelerator_ids.h
@@ -0,0 +1,32 @@
+// 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 ASH_MUS_ACCELERATORS_ACCELERATOR_IDS_H_
+#define ASH_MUS_ACCELERATORS_ACCELERATOR_IDS_H_
+
+namespace ash {
+namespace mus {
+
+// Accelerator ids consist of two parts:
+// . Upper 16 bits identifies source (namespace part).
+// . Lower 16 supplied from client (local part).
+constexpr uint16_t kLocalIdMask = 0xFFFF;
+
+inline uint32_t ComputeAcceleratorId(uint16_t accelerator_namespace,
+                                     uint16_t local_id) {
+  return (accelerator_namespace << 16) | local_id;
+}
+
+inline uint16_t GetAcceleratorLocalId(uint32_t accelerator_id) {
+  return static_cast<uint16_t>(accelerator_id & kLocalIdMask);
+}
+
+inline uint16_t GetAcceleratorNamespaceId(uint32_t accelerator_id) {
+  return static_cast<uint16_t>((accelerator_id >> 16) & kLocalIdMask);
+}
+
+}  // namespace mus
+}  // namespace ash
+
+#endif  // ASH_MUS_ACCELERATORS_ACCELERATOR_IDS_H_