Add a basic browser to mash that uses the navigation service.

mash/browser/browser.h

Index: mash/browser/browser.h
diff --git a/mash/browser/browser.h b/mash/browser/browser.h
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+++ b/mash/browser/browser.h
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+// 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 MASH_BROWSER_BROWSER_H_
+#define MASH_BROWSER_BROWSER_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "mash/public/interfaces/launchable.mojom.h"
+#include "mojo/public/cpp/bindings/binding_set.h"
+#include "services/shell/public/cpp/shell_client.h"
+#include "services/tracing/public/cpp/tracing_impl.h"
+
+namespace views {
+class AuraInit;
+class Widget;
+}
+
+namespace mash {
+namespace browser {
+
+class Browser
+    : public shell::ShellClient,
+      public mojom::Launchable,
+      public shell::InterfaceFactory<mojom::Launchable> {
+ public:
+  Browser();
+  ~Browser() override;
+
+  void AddWindow(views::Widget* window);

[sky, 2016/05/16 15:31:58]

Document what the widgets are, and ownership.

+  void RemoveWindow(views::Widget* window);
+
+ private:
+  // shell::ShellClient:
+  void Initialize(shell::Connector* connector,
+                  const shell::Identity& identity,
+                  uint32_t id) override;
+  bool AcceptConnection(shell::Connection* connection) override;
+
+  // mojom::Launchable:
+  void Launch(uint32_t what, mojom::LaunchMode how) override;
+
+  // shell::InterfaceFactory<mojom::Launchable>:
+  void Create(shell::Connection* connection,
+              mojom::LaunchableRequest request) override;
+
+  shell::Connector* connector_ = nullptr;
+  mojo::BindingSet<mojom::Launchable> bindings_;
+  std::vector<views::Widget*> windows_;
+
+  mojo::TracingImpl tracing_;
+  std::unique_ptr<views::AuraInit> aura_init_;
+
+  DISALLOW_COPY_AND_ASSIGN(Browser);
+};
+
+}  // namespace browser
+}  // namespace mash
+
+#endif  // MASH_BROWSER_BROWSER_H_