Support WebP images in the IOSImageDecoderImpl

ios/chrome/browser/suggestions/ios_image_decoder_impl.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 IOS_CHROME_BROWSER_SUGGESTIONS_IOS_IMAGE_DECODER_IMPL_H_
 #define IOS_CHROME_BROWSER_SUGGESTIONS_IOS_IMAGE_DECODER_IMPL_H_
 
-#include "base/macros.h"
+#include "base/memory/ref_counted.h"
 #include "components/image_fetcher/image_decoder.h"
 
+namespace base {
+class TaskRunner;
+}
+
 namespace suggestions {
 
-class IOSImageDecoderImpl : public image_fetcher::ImageDecoder {
- public:
-  IOSImageDecoderImpl();
-  ~IOSImageDecoderImpl() override;
-
-  void DecodeImage(
-      const std::string& image_data,
-      const image_fetcher::ImageDecodedCallback& callback) override;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(IOSImageDecoderImpl);
-};
+// The IOSImageDecoderImpl class is in .mm file, so that it could be used in .cc
+// files through the function below.
+std::unique_ptr<image_fetcher::ImageDecoder> createIOSImageDecoder(
+    const scoped_refptr<base::TaskRunner>& task_runner);
 
 }  // namespace suggestions
 
 #endif  // IOS_CHROME_BROWSER_SUGGESTIONS_IOS_IMAGE_DECODER_IMPL_H_