Use IOSImageDataFetcherWrapper for favicon

components/image_fetcher/image_data_fetcher.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 COMPONENTS_IMAGE_FETCHER_IMAGE_DATA_FETCHER_H_
 #define COMPONENTS_IMAGE_FETCHER_IMAGE_DATA_FETCHER_H_
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "components/data_use_measurement/core/data_use_user_data.h"
 #include "components/image_fetcher/request_metadata.h"
+#include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_fetcher_delegate.h"
 #include "net/url_request/url_request.h"
 #include "url/gurl.h"
 
 namespace net {
 class URLFetcher;
 class URLRequestContextGetter;
 }  // namespace net
 
 namespace image_fetcher {
 
 class ImageDataFetcher : public net::URLFetcherDelegate {
  public:
+  // Impossible http response code. Used to signal that no http response code
+  // was received.
+  enum ResponseCode {
+    RESPONSE_CODE_INVALID = net::URLFetcher::RESPONSE_CODE_INVALID
+  };
+
+  // Callback with the |image_data|. If an error prevented a http response,
+  // |request_metadata.response_code| will be RESPONSE_CODE_INVALID.
   using ImageDataFetcherCallback =
       base::Callback<void(const std::string& image_data,
                           const RequestMetadata& request_metadata)>;
 
   using DataUseServiceName = data_use_measurement::DataUseUserData::ServiceName;
 
   explicit ImageDataFetcher(
       net::URLRequestContextGetter* url_request_context_getter);
   ~ImageDataFetcher() override;
 
@@ skipping 32 matching lines @@
   // get individual URLFetchers and modify their state. Outside of tests this ID
   // is not used.
   int next_url_fetcher_id_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageDataFetcher);
 };
 
 }  // namespace image_fetcher
 
 #endif  // COMPONENTS_IMAGE_FETCHER_IMAGE_DATA_FETCHER_H_