Cleanup mojo_shell and sample_app a bit

mojo/shell/loader.h

+// Copyright 2013 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_LOADER_H_
+#define MOJO_SHELL_LOADER_H_
+
+#include "base/files/file_path.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/thread.h"
+#include "mojo/shell/url_request_context_getter.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "url/gurl.h"
+
+namespace mojo {
+namespace shell {
+
+class Loader {
+ public:
+  class Delegate {
+   public:
+    virtual void DidCompleteLoad(const GURL& app_url,
+                                 const base::FilePath& app_path) = 0;
+
+   protected:
+    virtual ~Delegate();
+  };
+
+  class Job : public net::URLFetcherDelegate {
+   public:
+    // You can cancel a job by deleting it.
+    virtual ~Job();
+
+   private:
+    friend class Loader;
+
+    // You can create a job using Loader::Load.
+    Job(const GURL& app_url, Delegate* delegate);
+    virtual void OnURLFetchComplete(const net::URLFetcher* source) OVERRIDE;
+
+    scoped_ptr<net::URLFetcher> fetcher_;
+    Delegate* delegate_;
+
+    DISALLOW_COPY_AND_ASSIGN(Job);
+  };
+
+  Loader(base::SingleThreadTaskRunner* network_runner,
+         base::SingleThreadTaskRunner* file_runner,
+         base::FilePath base_path);
+  ~Loader();
+
+  scoped_ptr<Job> Load(const GURL& app_url, Delegate* delegate);
+
+ private:
+  scoped_refptr<base::SingleThreadTaskRunner> file_runner_;
+  scoped_ptr<base::Thread> cache_thread_;
+  scoped_refptr<URLRequestContextGetter> url_request_context_getter_;
+
+  DISALLOW_COPY_AND_ASSIGN(Loader);
+};
+
+}  // namespace shell
+}  // namespace mojo
+
+#endif  // MOJO_SHELL_LOADER_H_