Reland: Split the code for fetching images and for decoding images into two separate classes. This w

chrome/browser/search/suggestions/image_decoder_impl.cc

+// 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.
+
+#include <algorithm>
+#include <vector>
+
+#include "chrome/browser/search/suggestions/image_decoder_impl.h"
+#include "ui/gfx/image/image.h"
+
+namespace suggestions {
+
+// A request for decoding an image.
+class ImageDecoderImpl::DecodeImageRequest
+    : public ::ImageDecoder::ImageRequest {
+ public:
+  DecodeImageRequest(ImageDecoderImpl* decoder,
+                     const image_fetcher::ImageDecodedCallback& callback)
+      : decoder_(decoder), callback_(callback) {}
+  ~DecodeImageRequest() override {}
+
+ private:
+  // Runs the callback and remove the request from the internal request queue.
+  void RunCallbackAndRemoveRequest(const gfx::Image& image);
+
+  // Methods inherited from ImageDecoder::ImageRequest
+
+  void OnImageDecoded(const SkBitmap& decoded_image) override;
+
+  void OnDecodeImageFailed() override;
+
+  ImageDecoderImpl* decoder_;
+
+  // The callback to call after the request completed.
+  image_fetcher::ImageDecodedCallback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(DecodeImageRequest);
+};
+
+void ImageDecoderImpl::DecodeImageRequest::OnImageDecoded(
+    const SkBitmap& decoded_bitmap) {
+  // TODO(markusheintz): Check whether high res displays that require 2x and 3x
+  // image versions need to be supported here.
+  gfx::Image image(gfx::Image::CreateFrom1xBitmap(decoded_bitmap));
+  RunCallbackAndRemoveRequest(image);
+}
+
+// Called when decoding image failed.
+void ImageDecoderImpl::DecodeImageRequest::OnDecodeImageFailed() {
+  RunCallbackAndRemoveRequest(gfx::Image());
+}
+
+void ImageDecoderImpl::DecodeImageRequest::RunCallbackAndRemoveRequest(
+    const gfx::Image& image) {
+  callback_.Run(image);
+
+  // This must be the last line in the method body.
+  decoder_->RemoveDecodeImageRequest(this);
+}
+
+ImageDecoderImpl::ImageDecoderImpl()  {}
+
+ImageDecoderImpl::~ImageDecoderImpl() {}
+
+void ImageDecoderImpl::DecodeImage(
+    const std::string& image_data,
+    const image_fetcher::ImageDecodedCallback& callback) {
+  std::unique_ptr<DecodeImageRequest> decode_image_request(
+      new DecodeImageRequest(this, callback));
+
+  ::ImageDecoder::Start(decode_image_request.get(), image_data);
+
+  decode_image_requests_.push_back(std::move(decode_image_request));
+}
+
+void ImageDecoderImpl::RemoveDecodeImageRequest(DecodeImageRequest* request) {
+  // Remove the finished request from the request queue.
+  auto request_it =
+      std::find_if(decode_image_requests_.begin(),
+                   decode_image_requests_.end(),
+                   [request](const std::unique_ptr<DecodeImageRequest>& r) {
+                     return r.get() == request;
+                   });
+  DCHECK(request_it != decode_image_requests_.end());
+  decode_image_requests_.erase(request_it);
+}
+
+}  // namespace suggestions