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

chrome/browser/predictors/resource_prefetcher_manager.cc

+// Copyright (c) 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_prefetcher_manager.h"
+
+#include "base/bind.h"
+#include "base/stl_util.h"
+#include "chrome/browser/predictors/resource_prefetch_predictor.h"
+#include "content/public/browser/browser_thread.h"
+#include "net/url_request/url_request.h"
+#include "net/url_request/url_request_context_getter.h"
+
+using content::BrowserThread;
+
+namespace predictors {
+
+ResourcePrefetcherManager::ResourcePrefetcherManager(
+    ResourcePrefetchPredictor* predictor,
+    const ResourcePrefetchPredictorConfig& config,
+    net::URLRequestContextGetter* context_getter)
+    : predictor_(predictor),
+      config_(config),
+      context_getter_(context_getter) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  CHECK(predictor_);
+  CHECK(context_getter_);
+}
+
+ResourcePrefetcherManager::~ResourcePrefetcherManager() {
+  DCHECK(prefetcher_map_.empty())
+      << "Did not call ShutdownOnUIThread or ShutdownOnIOThread. "
+         " Will leak Prefetcher pointers.";
+}
+
+void ResourcePrefetcherManager::ShutdownOnUIThread() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  predictor_ = NULL;
+  BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+      base::Bind(&ResourcePrefetcherManager::ShutdownOnIOThread,
+                 this));
+}
+
+void ResourcePrefetcherManager::ShutdownOnIOThread() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  STLDeleteContainerPairSecondPointers(prefetcher_map_.begin(),
+                                       prefetcher_map_.end());
+}
+
+void ResourcePrefetcherManager::MaybeAddPrefetch(
+    const NavigationID& navigation_id,
+    PrefetchKeyType key_type,
+    scoped_ptr<ResourcePrefetcher::RequestVector> requests) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  // Don't add a duplicate prefetch for the same host or URL.
+  std::string key = key_type == PREFETCH_KEY_TYPE_HOST ?
+      navigation_id.main_frame_url.host() : navigation_id.main_frame_url.spec();
+  PrefetcherMap::iterator prefetcher_it = prefetcher_map_.find(key);

[Lei Zhang, 2014/09/09 03:32:20]

nit: Use ContainsKey()

[Zhen Wang, 2014/09/13 00:36:33]

Done.

+  if (prefetcher_it != prefetcher_map_.end())
+    return;
+
+  ResourcePrefetcher* prefetcher = new ResourcePrefetcher(
+      this, config_, navigation_id, key_type, requests.Pass());
+  prefetcher_map_.insert(std::make_pair(key, prefetcher));
+  prefetcher->Start();
+}
+
+void ResourcePrefetcherManager::MaybeRemovePrefetch(
+    const NavigationID& navigation_id) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  // Look for a URL based prefetch first.
+  PrefetcherMap::iterator it = prefetcher_map_.find(
+      navigation_id.main_frame_url.spec());
+  if (it != prefetcher_map_.end() &&
+      it->second->navigation_id() == navigation_id) {
+    it->second->Stop();
+    return;
+  }
+
+  // No URL based prefetching, look for host based.
+  it = prefetcher_map_.find(navigation_id.main_frame_url.host());
+  if (it != prefetcher_map_.end() &&
+      it->second->navigation_id() == navigation_id) {
+    it->second->Stop();
+  }
+}
+
+void ResourcePrefetcherManager::ResourcePrefetcherFinished(
+    ResourcePrefetcher* resource_prefetcher,
+    ResourcePrefetcher::RequestVector* requests) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  // |predictor_| can only be accessed from the UI thread.
+  scoped_ptr<ResourcePrefetcher::RequestVector> requests_ptr(requests);

[Lei Zhang, 2014/09/09 03:32:20]

nit: |requests_ptr| is poorly named. It should be "scoped_requests". Or make the
parameter |requests_ptr| and change the scoper to "requests".

[Zhen Wang, 2014/09/13 00:36:33]

Done.

+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+      base::Bind(&ResourcePrefetcherManager::ResourcePrefetcherFinishedOnUI,
+                 this,
+                 resource_prefetcher->navigation_id(),
+                 resource_prefetcher->key_type(),
+                 base::Passed(&requests_ptr)));
+
+  const GURL& main_frame_url =
+      resource_prefetcher->navigation_id().main_frame_url;
+  const std::string key =
+      resource_prefetcher->key_type() == PREFETCH_KEY_TYPE_HOST ?
+          main_frame_url.host() : main_frame_url.spec();
+  PrefetcherMap::iterator it = prefetcher_map_.find(key);
+  DCHECK(it != prefetcher_map_.end());
+  delete it->second;
+  prefetcher_map_.erase(it);
+}
+
+void ResourcePrefetcherManager::ResourcePrefetcherFinishedOnUI(
+    const NavigationID& navigation_id,
+    PrefetchKeyType key_type,
+    scoped_ptr<ResourcePrefetcher::RequestVector> requests) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  // |predictor_| may have been set to NULL if the predictor is shutting down.
+  if (predictor_)

[Lei Zhang, 2014/09/09 03:32:20]

nit braces around multi-line if block contnets.

[Zhen Wang, 2014/09/13 00:36:33]

Done.

+    predictor_->FinishedPrefetchForNavigation(navigation_id,
+                                              key_type,
+                                              requests.release());
+}
+
+net::URLRequestContext* ResourcePrefetcherManager::GetURLRequestContext() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  return context_getter_->GetURLRequestContext();
+}
+
+}  // namespace predictors