Revert of Move fetching logic out of ApplicationManager, eliminate url mappings.

mojo/fetcher/about_fetcher.h

-// Copyright 2015 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_FETCHER_ABOUT_FETCHER_H_
-#define MOJO_FETCHER_ABOUT_FETCHER_H_
-
-#include "mojo/shell/fetcher.h"
-
-#include "base/macros.h"
-#include "mojo/services/network/public/interfaces/url_loader.mojom.h"
-#include "url/gurl.h"
-
-namespace mojo {
-namespace fetcher {
-
-// Implements Fetcher for about: URLs.
-class AboutFetcher : public shell::Fetcher {
- public:
-  static const char kAboutScheme[];
-  static const char kAboutBlankURL[];
-
-  static void Start(const GURL& url, const FetchCallback& loader_callback);
-
- private:
-  AboutFetcher(const GURL& url, const FetchCallback& loader_callback);
-  ~AboutFetcher() override;
-
-  void BuildResponse();
-
-  // Must be called exactly once to run the loader callback (asynchrously). On
-  // success, the ownership of this object is passed to the loader callback;
-  // otherwise, the callback is run with a nullptr and this object is destroyed.
-  void PostToRunCallback(bool success);
-
-  // shell::Fetcher implementation.
-  const GURL& GetURL() const override;
-  GURL GetRedirectURL() const override;
-  GURL GetRedirectReferer() const override;
-  URLResponsePtr AsURLResponse(base::TaskRunner* task_runner,
-                               uint32_t skip) override;
-  void AsPath(
-      base::TaskRunner* task_runner,
-      base::Callback<void(const base::FilePath&, bool)> callback) override;
-  std::string MimeType() override;
-  bool HasMojoMagic() override;
-  bool PeekFirstLine(std::string* line) override;
-
-  const GURL url_;
-  URLResponsePtr response_;
-
-  DISALLOW_COPY_AND_ASSIGN(AboutFetcher);
-};
-
-}  // namespace fetcher
-}  // namespace mojo
-
-#endif  // MOJO_FETCHER_ABOUT_FETCHER_H_