Add InterestsFetcher which retrieves a user's interests from the server.

chrome/browser/interests/interests_retriever.h

+// Copyright 2015 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 CHROME_BROWSER_INTERESTS_INTERESTS_RETRIEVER_H_
+#define CHROME_BROWSER_INTERESTS_INTERESTS_RETRIEVER_H_
+
+#include <string>
+#include <vector>
+
+#include "base/callback.h"
+#include "base/gtest_prod_util.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+#include "net/url_request/url_fetcher_factory.h"
+
+FORWARD_DECLARE_TEST(InterestsRetrieverTest, DefaultFakeResponse);
+
+// Class to asynchronously retrieve the topics of interests for a user.
+// Authentication is done using the user's OAUTH access_token.

[Marc Treib, 2015/09/03 15:35:06]

nit: OAuth

[tache, 2015/09/03 16:25:30]

Done.

+//
+// Example Usage:
+//
+// auto request = scoped_ptr<InterestsRetriever>(new InterestsRetriever(

[Marc Treib, 2015/09/03 15:35:06]

make_scoped_ptr(new ...
then you don't have to write "InterestsRetriever" twice. :)

Mention what happens when request is deleted before callback is called?

[tache, 2015/09/03 16:25:30]

Done.

+//    "user_access_token",
+//    callback));
+//
+class InterestsRetriever : public net::URLFetcherDelegate {

[Marc Treib, 2015/09/03 15:35:06]

Hm, "Fetcher" is much more common in Chromium than "Retriever". I realize it's a
bunch of work, but can we rename this?

[tache, 2015/09/03 16:25:30]

Done.

+ public:
+  struct Interest {
+    std::string name;
+    std::string image_url;
+    double relevance;
+
+    bool operator==(const Interest& interest) const;
+  };
+
+  typedef base::Callback<void(const std::vector<Interest>&)>
+      InterestsCallback;
+
+  InterestsRetriever(net::URLRequestContextGetter* url_request_context,
+                     const std::string& access_token,
+                     const InterestsCallback& callback,
+                     net::URLFetcherFactory* url_fetcher_factory);
+
+  ~InterestsRetriever() override;
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(::InterestsRetrieverTest, DefaultFakeResponse);
+
+  // net::URLFetcherDelegate implementation.
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  scoped_ptr<net::URLFetcher> CreateFetcher();
+
+  // parse the json response
+  std::vector<Interest> ExtractInterests(const std::string& response);
+
+  //
+  // Currently the InterestsRetreiever servers a static response since the API

[Marc Treib, 2015/09/03 15:35:06]

s/servers/serves/g

[tache, 2015/09/03 16:25:30]

Done.

+  // is not ready yet.
+  // This method is needed to access the static response in tests.
+  //
+  // TODO(tache): Remove this once the API is ready.
+  //
+  static std::string GetFakeResponseForTest();
+
+  net::URLRequestContextGetter* url_request_context_;
+
+  std::string access_token_;
+
+  InterestsCallback callback_;
+
+  scoped_ptr<net::URLFetcher> fetcher_;
+
+  net::URLFetcherFactory* url_fetcher_factory_;
+
+
+  DISALLOW_COPY_AND_ASSIGN(InterestsRetriever);
+};
+
+#endif  // CHROME_BROWSER_INTERESTS_INTERESTS_RETRIEVER_H_