Make SDCH dictionaries persistent across browser restart.

net/url_request/sdch_dictionary_fetcher.h

 // Copyright 2014 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.
 
 // TODO(rdsmith): This class needs to delegate URLRequest::Delegate methods
 // to the net/ embedder for correct implementation of authentication.
 // Specifically, this class needs the embedder to provide functionality
 // corresponding to
 // URLRequest::Delegate::{OnAuthRequired,OnCertificateRequested}.
 
@@ skipping 17 matching lines @@
 class URLRequestThrottlerEntryInterface;
 
 // This class is used by embedder SDCH policy object to fetch
 // dictionaries. It queues requests for dictionaries and dispatches
 // them serially, implementing the URLRequest::Delegate interface to
 // handle callbacks (but see above TODO). It tracks all requests, only
 // attempting to fetch each dictionary once.
 class NET_EXPORT SdchDictionaryFetcher : public URLRequest::Delegate,
                                          public base::NonThreadSafe {
  public:
+  class Data {
+   public:
+    virtual ~Data() {}
+  };
+
   typedef base::Callback<void(const std::string& dictionary_text,
                               const GURL& dictionary_url,
+                              scoped_ptr<Data> extra_data,
                               const BoundNetLog& net_log)>
       OnDictionaryFetchedCallback;
 
   // The consumer must guarantee that |*context| outlives this object.
   // |callback| will be called on successful dictionary fetch
   // requested through Schedule().  |callback| will not be called
   // after object destruction.
   SdchDictionaryFetcher(URLRequestContext* context,
                         const OnDictionaryFetchedCallback& callback);
   ~SdchDictionaryFetcher() override;
 
-  // Request a new dictionary fetch.
-  void Schedule(const GURL& dictionary_url);
+  // Request a new dictionary fetch.  |extra_data| is data that will be
+  // returned in the OnDictionaryFetchedCallback if the dictionary fetch
+  // succeeds; otherwise it will be destroyed.
+  void Schedule(const GURL& dictionary_url, scoped_ptr<Data> extra_data);
+
+  // Request a dictionary fetch from cache only.  See comment above
+  // for information on |extra_data|.
+  void ScheduleReload(const GURL& dictionary_url, scoped_ptr<Data> extra_data);
 
   // Cancel any in-progress requests.
   void Cancel();
 
   // Implementation of URLRequest::Delegate methods.
   void OnResponseStarted(URLRequest* request) override;
   void OnReadCompleted(URLRequest* request, int bytes_read) override;
 
  private:
   enum State {
     STATE_NONE,
     STATE_IDLE,
     STATE_REQUEST_STARTED,
     STATE_REQUEST_READING,
     STATE_REQUEST_COMPLETE,
   };
 
+  struct QueuedInfo {
+    const GURL url;
+    bool download_only_from_cache;
+
+    // Owned by |fetch_queue_|; must be destroyed if queue entry is
+    // dropped.  Not a scoped_ptr<> as std::queue requires copyable
+    // types.
+    Data* extra_data;
+
+    QueuedInfo() : download_only_from_cache(false), extra_data(nullptr) {}
+    QueuedInfo(const GURL& url,
+               bool download_only_from_cache,
+               scoped_ptr<Data> extra_data);
+    QueuedInfo(const QueuedInfo& rhs) = default;
+    QueuedInfo& operator=(const QueuedInfo& rhs) = default;
+  };
+
+  // Schedule implementation.
+  void ScheduleInternal(const GURL& dictionary_url,
+                        bool reload,
+                        scoped_ptr<Data> extra_data);
+
+  // Null out the current request and push the state machine to the
+  // next request, if any.
+  void ResetRequest();
+
   // State machine implementation.
   int DoLoop(int rv);
   int DoDispatchRequest(int rv);
   int DoRequestStarted(int rv);
   int DoRead(int rv);
   int DoCompleteRequest(int rv);
 
   State next_state_;
   bool in_loop_;
 
   // A queue of URLs that are being used to download dictionaries.
-  std::queue<GURL> fetch_queue_;
+  // |fetch_queue_[n].second| indicated whether the download should occur
+  // only from cache.
+  std::queue<QueuedInfo> fetch_queue_;
 
-  // The request and buffer used for getting the current dictionary
-  // Both are null when a fetch is not in progress.
+  // The request, buffer, and consumer supplied data used for getting
+  // the current dictionary.  All are null when a fetch is not in progress.
   scoped_ptr<URLRequest> current_request_;
   scoped_refptr<IOBuffer> buffer_;
+  scoped_ptr<Data> current_extra_data_;
 
   // The currently accumulating dictionary.
   std::string dictionary_;
 
   // Althought the SDCH spec does not preclude a server from using a single URL
   // to load several distinct dictionaries (by telling a client to load a
   // dictionary from an URL several times), current implementations seem to have
   // that 1-1 relationship (i.e., each URL points at a single dictionary, and
   // the dictionary content does not change over time, and hence is not worth
   // trying to load more than once). In addition, some dictionaries prove
@@ skipping 13 matching lines @@
   const OnDictionaryFetchedCallback dictionary_fetched_callback_;
 
   base::WeakPtrFactory<SdchDictionaryFetcher> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SdchDictionaryFetcher);
 };
 
 }  // namespace net
 
 #endif  // NET_URL_REQUEST_SDCH_DICTIONARY_FETCHER_H_