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

chrome/browser/interests/interests_fetcher.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_FETCHER_H_
+#define CHROME_BROWSER_INTERESTS_INTERESTS_FETCHER_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 "chrome/browser/profiles/profile.h"
+#include "components/signin/core/browser/signin_manager.h"
+#include "google_apis/gaia/oauth2_token_service.h"
+#include "net/url_request/url_fetcher.h"
+#include "net/url_request/url_fetcher_delegate.h"
+
+// Class to fetch a user's interests as computed by Google Now. Each interest is
+// represented as a tuple of its name, an url to a representative image, and a
+// score measuring the level of interest of the user.
+//
+// Authentication is done via OAuth2 and requires the
+// https://www.googleapis.com/auth/googlenow scope.
+//
+// If the InterestsFetcher is deleted before the callback is called then the
+// request will be aborted.
+//

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

please remove the example usage part of the comment. it's redundant with the
code, and actually already now wrong...

[PEConn, 2015/10/05 14:12:05]

Done.

+// Example Usage:
+//
+// auto request = make_scoped_ptr(new InterestsFetcher(callback));
+//
+class InterestsFetcher : public net::URLFetcherDelegate,
+                         public OAuth2TokenService::Consumer {
+ public:
+  struct Interest {
+    std::string name;
+    GURL image_url;
+    double relevance;
+
+    Interest(const std::string& name, const GURL& image_url, float rlevance);

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

ctor and dtor should come before data members:
https://google-styleguide.googlecode.com/svn/trunk/cppguide.html#Declaration_...

also, spelling: relevance

[PEConn, 2015/10/05 14:12:04]

Done.

+

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

no empty line here

[PEConn, 2015/10/05 14:12:04]

Done.

+    ~Interest();
+
+    bool operator==(const Interest& interest) const;
+  };
+
+  typedef base::Callback<void(const std::vector<Interest>&)>
+      InterestsCallback;
+
+  InterestsFetcher(
+      OAuth2TokenService* oauth2_token_service,

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

how do you guarantee that the token service is still alive by the time you use
it? Why not pass it as a parameter to Start()?

[PEConn, 2015/10/05 14:12:04]

The token service needs to be stored so we can retry things on an authorization
error.
The token service is tied to the Profile and since the InterestsFetcher should
be shorter lived than the profile, this shouldn't be an issue.

+      const std::string& account_id,
+      net::URLRequestContextGetter* context);
+
+  ~InterestsFetcher() override;
+
+  static scoped_ptr<InterestsFetcher> CreateFromProfile(Profile* profile);

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

can you have multiple fetchers per profile? Should this be a
profile-keyed-service? should the ctor be private?

[PEConn, 2015/10/05 14:12:04]

You can have multiple fetchers per profile.
It's perfectly valid for a user to create a InterestsFetcher from its
constructor, the 'CreateFromProfile' method is just for convenience.

+
+  void Start(const InterestsCallback& callback);

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

this could use a comment what it starts (or a better name - StartFetching)

[PEConn, 2015/10/05 14:12:04]

Done.

+
+ private:
+  // net::URLFetcherDelegate implementation.
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  // OAuth2TokenService::Consumer implementation.
+  void OnGetTokenSuccess(const OAuth2TokenService::Request* request,
+                         const std::string& access_token,
+                         const base::Time& experiation_time) override;
+

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

no empty line here

[PEConn, 2015/10/05 14:12:05]

Done.

+  void OnGetTokenFailure(const OAuth2TokenService::Request* request,
+                         const GoogleServiceAuthError& error) override;
+
+  void StartOAuth2Request();
+

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

no empty line here

[PEConn, 2015/10/05 14:12:05]

Done.

+  OAuth2TokenService::ScopeSet GetApiScopes();
+

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

nor here

[PEConn, 2015/10/05 14:12:05]

Done.

+  scoped_ptr<net::URLFetcher> CreateFetcher();
+
+  // Parse the json response.
+  std::vector<Interest> ExtractInterests(const std::string& response);
+
+  InterestsCallback callback_;
+
+  scoped_ptr<net::URLFetcher> fetcher_;

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

sooo many empty lines here.

[PEConn, 2015/10/05 14:12:04]

Done.

+
+  scoped_ptr<OAuth2TokenService::Request> oauth_request_;
+
+  OAuth2TokenService* token_service_;
+
+  std::string account_id_;
+
+  net::URLRequestContextGetter* url_request_context_;
+
+  bool access_token_expired_;
+
+  std::string access_token_;
+
+

[jochen (gone - plz use gerrit), 2015/10/02 13:51:00]

only one empty line here

[PEConn, 2015/10/05 14:12:05]

Done.

+  DISALLOW_COPY_AND_ASSIGN(InterestsFetcher);
+};
+
+#endif  // CHROME_BROWSER_INTERESTS_INTERESTS_FETCHER_H_