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

chrome/browser/predictors/resource_prefetch_predictor_factory.cc

-// 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.
-
-#include "chrome/browser/predictors/resource_prefetch_predictor_factory.h"
-
-#include "chrome/browser/history/history_service_factory.h"
-#include "chrome/browser/predictors/predictor_database_factory.h"
-#include "chrome/browser/predictors/resource_prefetch_common.h"
-#include "chrome/browser/predictors/resource_prefetch_predictor.h"
-#include "chrome/browser/profiles/profile.h"
-#include "components/keyed_service/content/browser_context_dependency_manager.h"
-#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
-
-namespace predictors {
-
-// static
-ResourcePrefetchPredictor* ResourcePrefetchPredictorFactory::GetForProfile(
-    content::BrowserContext* context) {
-  return static_cast<ResourcePrefetchPredictor*>(
-      GetInstance()->GetServiceForBrowserContext(context, true));
-}
-
-// static
-ResourcePrefetchPredictorFactory*
-ResourcePrefetchPredictorFactory::GetInstance() {
-  return Singleton<ResourcePrefetchPredictorFactory>::get();
-}
-
-ResourcePrefetchPredictorFactory::ResourcePrefetchPredictorFactory()
-    : BrowserContextKeyedServiceFactory(
-        "ResourcePrefetchPredictor",
-        BrowserContextDependencyManager::GetInstance()) {
-  DependsOn(HistoryServiceFactory::GetInstance());
-  DependsOn(PredictorDatabaseFactory::GetInstance());
-}
-
-ResourcePrefetchPredictorFactory::~ResourcePrefetchPredictorFactory() {}
-
-KeyedService*
-    ResourcePrefetchPredictorFactory::BuildServiceInstanceFor(
-        content::BrowserContext* context) const {
-  Profile* profile = Profile::FromBrowserContext(context);
-
-  ResourcePrefetchPredictorConfig config;
-  if (!IsSpeculativeResourcePrefetchingEnabled(profile, &config))
-    return NULL;
-
-  return new ResourcePrefetchPredictor(config, profile);
-}
-
-}  // namespace predictors