Mojo: Add some tests for ChannelEndpointId, etc.

mojo/edk/system/channel_endpoint_id.cc

+// Copyright 2014 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 "mojo/edk/system/channel_endpoint_id.h"
+
+namespace mojo {
+namespace system {
+
+ChannelEndpointId LocalChannelEndpointIdGenerator::GetNext() {
+  ChannelEndpointId rv = next_channel_endpoint_id_;
+  next_channel_endpoint_id_.value_++;
+  // Skip over the invalid value, in case we wrap.
+  if (!next_channel_endpoint_id_.is_valid())
+    next_channel_endpoint_id_.value_++;
+  return rv;
+}
+
+}  // namespace system
+}  // namespace mojo