Use mime type for image extension

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..ac32aa04c63f0be0e6540e0a653546c43cd7451a 100644
--- a/components/image_fetcher/image_data_fetcher.h
+++ b/components/image_fetcher/image_data_fetcher.h
@@ -24,10 +24,21 @@ class URLRequestContextGetter;
 
 namespace image_fetcher {
 
+struct RequestMetadata {

[gambard, 2017/02/09 13:44:12]

I don't know if this should be inside the class?

[Marc Treib, 2017/02/09 13:49:48]

That's mostly a matter of taste IMO. I tend to slightly prefer the nested class
approach, but I don't feel very strongly.

[sdefresne, 2017/02/09 13:55:28]

drive-by: having the class separate make it easier to refactor code or break
dependencies as it allows you to 1. forward-declare it (it is not possible to
forward-declare nested classes outside of the outer class declaration), 2. move
it to a separate file (allowing you to just include the header for that class if
you do not care about the outer class).

[gambard, 2017/02/09 15:10:32]

Actually, I have moved it to its own class.

[gambard, 2017/02/09 15:10:32]

Ok, I think I will let it outside the class as it is also used by the
IOSImageDataWrapper.

+  std::string mime_type;
+
+  bool operator==(const RequestMetadata& rhs) const {

[Marc Treib, 2017/02/09 13:49:48]

Are the equality operators required?

[sdefresne, 2017/02/09 13:55:28]

Even if they are required, they generally do not need to be methods but can be
free functions instead:

struct RequestMetaData {
  ...
};

bool operator==(const RequestMetaData& lhs, const RequestMetadata& rhs) {
  return ...
}

[gambard, 2017/02/09 15:10:32]

They are mainly here for testing (verifying that the received metadata is the
expected one).

+    return mime_type == rhs.mime_type;
+  }
+
+  bool operator!=(const RequestMetadata& rhs) const { return !operator==(rhs); }
+};
+
 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 RequestMetadata& request_metadata)>;
 
   using DataUseServiceName = data_use_measurement::DataUseUserData::ServiceName;