Set desired_image_size when decoding images for NTP Tile icons.

components/image_fetcher/image_decoder.h

Index: components/image_fetcher/image_decoder.h
diff --git a/components/image_fetcher/image_decoder.h b/components/image_fetcher/image_decoder.h
index 904830cb0cb42c43b5a6bf0b02e5903f0ab98881..b5589f17b4a9b69cfa80cc45a0c89466567867aa 100644
--- a/components/image_fetcher/image_decoder.h
+++ b/components/image_fetcher/image_decoder.h
@@ -12,6 +12,7 @@
 
 namespace gfx {
 class Image;
+class Size;
 }  // namespace gfx
 
 namespace image_fetcher {
@@ -27,7 +28,13 @@ class ImageDecoder {
   // Decodes the passed |image_data| and runs the given callback. The callback
   // is run even if decoding the image fails. In case an error occured during
   // decoding the image an empty image is passed to the callback.
+  // For images with multiple frames (e.g. ico files), a frame with a size as
+  // close as possible to |desired_image_frame_size| is chosen (tries to take
+  // one in larger size if there's no precise match). Passing gfx::Size() as
+  // |desired_image_frame_size| is also supported and will result in chosing the
+  // smallest available size.
   virtual void DecodeImage(const std::string& image_data,
+                           const gfx::Size& desired_image_frame_size,
                            const ImageDecodedCallback& callback) = 0;
 
  private: