mojo: Add DataURLFetcher for processing data: urls.

mojo/fetcher/data_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_
+#ifndef MOJO_FETCHER_DATA_FETCHER_H_
+#define MOJO_FETCHER_DATA_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 {
+// Implements Fetcher for data: URLs.
+class DataFetcher : 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;
+  DataFetcher(const GURL& url, const FetchCallback& loader_callback);
+  ~DataFetcher() 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);
+  void BuildAndDispatchResponse();
 
   // 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);
+  DISALLOW_COPY_AND_ASSIGN(DataFetcher);
 };
 
 }  // namespace fetcher
 }  // namespace mojo
 
-#endif  // MOJO_FETCHER_ABOUT_FETCHER_H_
+#endif  // MOJO_FETCHER_DATA_FETCHER_H_