Add a instance groups to Connect(), and introduce an Identity struct.

mojo/shell/public/cpp/lib/identity.cc

+// 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.
+
+#include "mojo/shell/public/cpp/identity.h"
+
+#include "base/guid.h"
+#include "mojo/shell/public/cpp/names.h"
+
+namespace mojo {
+
+Identity::Identity() {}
+
+Identity::Identity(const std::string& name, const std::string& user_id)
+    : Identity(name, user_id, "") {}
+
+Identity::Identity(const std::string& name, const std::string& user_id,
+                   const std::string& instance)
+    : name_(name),
+      user_id_(user_id),
+      instance_(instance.empty() ? GetNamePath(name_) : instance) {
+  CHECK(!user_id.empty());
+  CHECK(base::IsValidGUID(user_id));
+}
+
+Identity::Identity(const Identity& other) = default;
+
+Identity::~Identity() {}
+
+bool Identity::operator<(const Identity& other) const {
+  if (name_ != other.name_)
+    return name_ < other.name_;
+  if (instance_ != other.instance_)
+    return instance_ < other.instance_;
+  return user_id_ < other.user_id_;
+}
+
+bool Identity::operator==(const Identity& other) const {
+  return other.name_ == name_ && other.instance_ == instance_ &&
+         other.user_id_ == user_id_;
+}
+
+// static
+shell::mojom::IdentityPtr
+    TypeConverter<shell::mojom::IdentityPtr, Identity>::Convert(
+        const Identity& input) {
+  shell::mojom::IdentityPtr identity(shell::mojom::Identity::New());
+  identity->name = input.name();
+  identity->user_id = input.user_id();
+  identity->instance = input.instance();
+  return identity;
+}
+
+// static
+Identity TypeConverter<Identity, shell::mojom::IdentityPtr>::Convert(
+    const shell::mojom::IdentityPtr& input) {
+  return Identity(input->name, input->user_id, input->instance);
+}
+
+}  // namespace mojo