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

chrome/browser/interests/interests_fetcher.h

Index: chrome/browser/interests/interests_fetcher.h
diff --git a/chrome/browser/interests/interests_fetcher.h b/chrome/browser/interests/interests_fetcher.h
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+++ b/chrome/browser/interests/interests_fetcher.h
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+// 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 topics of interest for a user as computed by Google Now. Each
+// interest is a tuple of a name, a thumbnail URL and a relevance score. This
+// class is one-shot. To retrieve interests multiple times use multiple
+// instances of this class.
+//
+// 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. It is up to the user to ensure that both the
+// Profile and the OAuth2TokenService outlive the InterestsFetcher.
+//
+// The server required for this feature is not publicly available yet.
+class InterestsFetcher : public net::URLFetcherDelegate,
+                         public OAuth2TokenService::Consumer {
+ public:
+  struct Interest {
+    Interest(const std::string& name, const GURL& image_url, double relevance);
+    ~Interest();
+
+    bool operator==(const Interest& interest) const;
+
+    std::string name;
+    GURL image_url;
+    double relevance;
+  };
+
+  using InterestsCallback = base::Callback<void(const std::vector<Interest>&)>;
+
+  InterestsFetcher(OAuth2TokenService* oauth2_token_service,
+                   const std::string& account_id,
+                   net::URLRequestContextGetter* context);
+
+  ~InterestsFetcher() override;
+
+  static scoped_ptr<InterestsFetcher> CreateFromProfile(Profile* profile);
+
+  void FetchInterests(const InterestsCallback& callback);
+
+ 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;
+  void OnGetTokenFailure(const OAuth2TokenService::Request* request,
+                         const GoogleServiceAuthError& error) override;
+
+  void StartOAuth2Request();
+  OAuth2TokenService::ScopeSet GetApiScopes();
+  scoped_ptr<net::URLFetcher> CreateFetcher();
+
+  // Parse the json response.
+  std::vector<Interest> ExtractInterests(const std::string& response);
+
+  InterestsCallback callback_;
+  scoped_ptr<net::URLFetcher> fetcher_;
+  std::string account_id_;
+  net::URLRequestContextGetter* url_request_context_;
+  bool access_token_expired_;
+  std::string access_token_;
+
+  scoped_ptr<OAuth2TokenService::Request> oauth_request_;
+  OAuth2TokenService* token_service_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterestsFetcher);
+};
+
+#endif  // CHROME_BROWSER_INTERESTS_INTERESTS_FETCHER_H_