Create the IOSImageDataFetcher

components/image_fetcher/image_data_fetcher.h

Index: components/image_fetcher/image_data_fetcher.h
diff --git a/components/image_fetcher/image_data_fetcher.h b/components/image_fetcher/image_data_fetcher.h
index 92c5a5cf0dc233d7c004adc58387f336115361bf..e578ba0aa22136046784a1e3d7cc66b97374e4cf 100644
--- a/components/image_fetcher/image_data_fetcher.h
+++ b/components/image_fetcher/image_data_fetcher.h
@@ -26,7 +26,8 @@ namespace image_fetcher {
 class ImageDataFetcher : public net::URLFetcherDelegate {
  public:
   using ImageDataFetcherCallback =
-      base::Callback<void(const std::string& image_data)>;
+      base::Callback<void(const std::string& image_data,
+                          const net::URLFetcher* source)>;

[Marc Treib, 2017/01/25 10:37:55]

You'll have to update the tests for the new param. It'd also be great to add
some tests for the new behavior.

That said, this seems like a somewhat weird interface: This class is supposed to
abstract away the details of the URLFetcher etc.
What exact info does your client need? Would it be enough to return some sort of
error code instead of the URLFetcher?

[markusheintz_, 2017/01/25 12:03:45]

It would be great to learn what motivates this change.

[gambard, 2017/01/25 12:09:45]

The IOSImageDataFetcher class is using the URLFetcher to get the mime type (to
check if it is WebP), the http response (needed by some classes in the callback,
I need to add it) and the original url (to see if it is a data URI or not).
Considering that, I think I need it in the callback I am using to decode the
WebP. With the architecture as it is, it seemed to be the smallest change.

 
   using DataUseServiceName = data_use_measurement::DataUseUserData::ServiceName;