Revert of Revert CL 117933003. Re-add resource speculative prefetching code.

chrome/browser/net/resource_prefetch_predictor_observer.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.
-
-#ifndef CHROME_BROWSER_NET_RESOURCE_PREFETCH_PREDICTOR_OBSERVER_H_
-#define CHROME_BROWSER_NET_RESOURCE_PREFETCH_PREDICTOR_OBSERVER_H_
-
-#include "base/basictypes.h"
-#include "base/memory/weak_ptr.h"
-#include "chrome/browser/predictors/resource_prefetch_predictor.h"
-#include "content/public/common/resource_type.h"
-
-namespace net {
-class URLRequest;
-}
-
-class GURL;
-
-namespace chrome_browser_net {
-
-// Observes resource requests in the ResourceDispatcherHostDelegate and notifies
-// the ResourcePrefetchPredictor about the ones it is interested in.
-//  - Has an instance per profile, and is owned by the corresponding
-//    ProfileIOData.
-//  - Needs to be constructed on UI thread. Rest of the functions can only be
-//    called on the IO thread. Can be destroyed on UI or IO thread.
-class ResourcePrefetchPredictorObserver {
- public:
-  explicit ResourcePrefetchPredictorObserver(
-      predictors::ResourcePrefetchPredictor* predictor);
-  ~ResourcePrefetchPredictorObserver();
-
-  // Parts of the ResourceDispatcherHostDelegate that we want to observe.
-  void OnRequestStarted(net::URLRequest* request,
-                        content::ResourceType resource_type,
-                        int child_id,
-                        int frame_id);
-  void OnRequestRedirected(const GURL& redirect_url, net::URLRequest* request);
-  void OnResponseStarted(net::URLRequest* request);
-
- private:
-  // Owned by profile.
-  base::WeakPtr<predictors::ResourcePrefetchPredictor> predictor_;
-
-  DISALLOW_COPY_AND_ASSIGN(ResourcePrefetchPredictorObserver);
-};
-
-}  // namespace chrome_browser_net
-
-#endif  // CHROME_BROWSER_NET_RESOURCE_PREFETCH_PREDICTOR_OBSERVER_H_