components/image_fetcher: Expose RequestMetadata from ImageFetcher

components/image_fetcher/image_fetcher.h

 // Copyright 2014 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_FETCHER_H_
 #define COMPONENTS_IMAGE_FETCHER_IMAGE_FETCHER_H_
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "components/data_use_measurement/core/data_use_user_data.h"
 #include "components/image_fetcher/image_fetcher_delegate.h"
 #include "url/gurl.h"
 
 namespace gfx {
 class Image;
 class Size;
 }
 
 namespace image_fetcher {
 
 class ImageDecoder;
 
+struct RequestMetadata;
+
 // A class used to fetch server images. It can be called from any thread and the
 // callback will be called on the thread which initiated the fetch.
 class ImageFetcher {
  public:
   ImageFetcher() {}
   virtual ~ImageFetcher() {}
 
+  using ImageFetcherCallback =
+      base::Callback<void(const std::string& id,
+                          const gfx::Image& image,
+                          const RequestMetadata& metadata)>;

[jkrcal, 2017/03/20 10:49:59]

A nice cleanup!

+
   using DataUseServiceName = data_use_measurement::DataUseUserData::ServiceName;
 
   virtual void SetImageFetcherDelegate(ImageFetcherDelegate* delegate) = 0;
 
   // Sets a service name against which to track data usage.
   virtual void SetDataUseServiceName(
       DataUseServiceName data_use_service_name) = 0;
 
   // Sets the desired size for images with multiple frames (like .ico files).
   // By default, the image fetcher choses smaller images. Override to choose a
   // frame with a size as close as possible to |size| (trying to take one in
   // larger size if there's no precise match). Passing gfx::Size() as
   // |size| is also supported and will result in chosing the smallest available
   // size.
   virtual void SetDesiredImageFrameSize(const gfx::Size& size) = 0;
 
   // An empty gfx::Image will be returned to the callback in case the image
   // could not be fetched.
   virtual void StartOrQueueNetworkRequest(
       const std::string& id,
       const GURL& image_url,
-      base::Callback<void(const std::string&, const gfx::Image&)> callback) = 0;
+      const ImageFetcherCallback& callback) = 0;
 
   virtual ImageDecoder* GetImageDecoder() = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ImageFetcher);
 };
 
 }  // namespace image_fetcher
 
 #endif  // COMPONENTS_IMAGE_FETCHER_IMAGE_FETCHER_H_