Use IOSImageDataFetcherWrapper for favicon

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 5383086a519b2aa37324ab4335a5df99ef229d1e..b61f60e8ff5afef7cff093ae9a3079987558528e 100644
--- a/components/image_fetcher/image_data_fetcher.h
+++ b/components/image_fetcher/image_data_fetcher.h
@@ -13,6 +13,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "components/data_use_measurement/core/data_use_user_data.h"
+#include "net/url_request/url_fetcher.h"
 #include "net/url_request/url_fetcher_delegate.h"
 #include "net/url_request/url_request.h"
 #include "url/gurl.h"
@@ -26,8 +27,18 @@ namespace image_fetcher {
 
 class ImageDataFetcher : public net::URLFetcherDelegate {
  public:
+  // Imposible http response code. Used to signal that no http response code

[Marc Treib, 2017/02/07 10:10:21]

nit: Impossible

[sdefresne, 2017/02/07 10:18:30]

Imposible -> Impossible

[gambard, 2017/02/08 14:48:12]

Done.

+  // was received.
+  enum ResponseCode {
+    RESPONSE_CODE_INVALID = net::URLFetcher::RESPONSE_CODE_INVALID

[Marc Treib, 2017/02/07 10:10:21]

Hm, I'm not entirely convinced we want this alias. As far as I can tell, it's
currently not used anywhere, and anyway clients could just compare to
net::URLFetcher::RESPONSE_CODE_INVALID directly. (That's a bit ugly since it
kinda exposes implementation details of URLFetcher, but then the whole fake
response code is a bit of a hack, so...)

tl;dr I'd remove the alias, and mention net::URLFetcher::RESPONSE_CODE_INVALID
in the comment below. WDYT?

[Marc Treib, 2017/02/07 10:23:14]

As discussed out-of-band: I'm okay with the alias.

[gambard, 2017/02/08 14:48:12]

Acknowledged.

+  };
+
+  // Callback with the |image_data| and the |http_response_code|. If an error
+  // prevented a http response, |http_response_code| will be
+  // RESPONSE_CODE_INVALID.
   using ImageDataFetcherCallback =
-      base::Callback<void(const std::string& image_data)>;
+      base::Callback<void(const std::string& image_data,
+                          int http_response_code)>;
 
   using DataUseServiceName = data_use_measurement::DataUseUserData::ServiceName;