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

mojo/shell/public/cpp/shell_test.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 MOJO_SHELL_PUBLIC_CPP_SHELL_TEST_H_
 #define MOJO_SHELL_PUBLIC_CPP_SHELL_TEST_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "mojo/public/cpp/system/macros.h"
 #include "mojo/shell/public/cpp/connector.h"
@@ skipping 17 matching lines @@
 // to customize this should subclass this class instead of ShellClient,
 // otherwise they will have to call ShellTest::InitializeCalled() to forward
 // metadata from Initialize() to the test.
 class ShellTestClient : public mojo::ShellClient {
  public:
   explicit ShellTestClient(ShellTest* test);
   ~ShellTestClient() override;
 
  protected:
   void Initialize(Connector* connector,
-                  const std::string& name,
-                  const std::string& user_id,
+                  const Identity& identity,
                   uint32_t id) override;
 
  private:
   ShellTest* test_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellTestClient);
 };
 
 class ShellTest : public testing::Test {
  public:
@@ skipping 49 matching lines @@
   std::string initialize_userid_ = shell::mojom::kInheritUserID;
   uint32_t initialize_instance_id_ = shell::mojom::kInvalidInstanceID;
 
   DISALLOW_COPY_AND_ASSIGN(ShellTest);
 };
 
 }  // namespace test
 }  // namespace mojo
 
 #endif  // MOJO_SHELL_PUBLIC_CPP_SHELL_TEST_H_