Fetch SDCH dictionary as soon as current URL fetch completes...

chrome/browser/net/sdch_dictionary_fetcher.h

 // Copyright (c) 2006-2008 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.
 
 // Support modularity by calling to load a new SDCH filter dictionary.
 // Note that this sort of calling can't be done in the /net directory, as it has
 // no concept of the HTTP cache (which is only visible at the browser level).
 
 #ifndef CHROME_BROWSER_NET_SDCH_DICTIONARY_FETCHER_H_
 #define CHROME_BROWSER_NET_SDCH_DICTIONARY_FETCHER_H_
 
 #include <queue>
 #include <string>
 
 #include "base/compiler_specific.h"
+#include "base/scoped_ptr.h"
 #include "base/task.h"
 #include "chrome/browser/net/url_fetcher.h"
 #include "net/base/sdch_manager.h"
 
 class SdchDictionaryFetcher : public URLFetcher::Delegate,
                               public SdchFetcher {
  public:
-  SdchDictionaryFetcher() : 
+  SdchDictionaryFetcher() :
       ALLOW_THIS_IN_INITIALIZER_LIST(method_factory_(this)),
       task_is_pending_(false) {}
   virtual ~SdchDictionaryFetcher() {}
 
   // Implementation of SdchFetcher class.
   // This method gets the requested dictionary, and then calls back into the
   // SdchManager class with the dictionary's text.
   virtual void Schedule(const GURL& dictionary_url);
 
  private:
-  // Delay between Schedule and actual download.
-  static const int kMsDelayFromRequestTillDownload = 15000;
+  // Delay in ms between Schedule and actual download.
+  // This leaves the URL in a queue, which is de-duped, so that there is less
+  // chance we'll try to load the same URL multiple times when a pile of
+  // page subresources (or tabs opened in parallel) all suggest the dictionary.
+  static const int kMsDelayFromRequestTillDownload = 100;
 
   // Ensure the download after the above delay.
   void ScheduleDelayedRun();
 
   // Make sure we're processing (or waiting for) the the arrival of the next URL
   // in the  |fetch_queue_|.
   void StartFetching();
 
   // Implementation of URLFetcher::Delegate. Called after transmission
   // completes (either successfully or with failure).
@@ skipping 13 matching lines @@
   // Always spread out the dictionary fetches, so that they don't steal
   // bandwidth from the actual page load.  Create delayed tasks to spread out
   // the download.
   ScopedRunnableMethodFactory<SdchDictionaryFetcher> method_factory_;
   bool task_is_pending_;
 
   DISALLOW_COPY_AND_ASSIGN(SdchDictionaryFetcher);
 };
 
 #endif  // CHROME_BROWSER_NET_SDCH_DICTIONARY_FETCHER_H_