Cancel prerenders from Omnibox if we navigate to a different URL than predicted

chrome/browser/prerender/prerender_manager.cc

Index: chrome/browser/prerender/prerender_manager.cc
diff --git a/chrome/browser/prerender/prerender_manager.cc b/chrome/browser/prerender/prerender_manager.cc
index 59bb8609fd6a56cf8b05fb11f920b8a2b014b779..e52557c3721f09c43afdf9c3228e19f1a88cd2d2 100644
--- a/chrome/browser/prerender/prerender_manager.cc
+++ b/chrome/browser/prerender/prerender_manager.cc
@@ -153,52 +153,6 @@ int PrerenderManager::prerenders_per_session_count_ = 0;
 PrerenderManager::PrerenderManagerMode PrerenderManager::mode_ =
     PRERENDER_MODE_ENABLED;
 
-// static
-PrerenderManager::PrerenderManagerMode PrerenderManager::GetMode() {
-  return mode_;
-}
-
-// static
-void PrerenderManager::SetMode(PrerenderManagerMode mode) {
-  mode_ = mode;
-}
-
-// static
-bool PrerenderManager::IsPrerenderingPossible() {
-  return GetMode() == PRERENDER_MODE_ENABLED ||
-         GetMode() == PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP ||
-         GetMode() == PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP ||
-         GetMode() == PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP;
-}
-
-// static
-bool PrerenderManager::ActuallyPrerendering() {
-  return IsPrerenderingPossible() && !IsControlGroup();
-}
-
-// static
-bool PrerenderManager::IsControlGroup() {
-  return GetMode() == PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP;
-}
-
-// static
-bool PrerenderManager::IsNoUseGroup() {
-  return GetMode() == PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP;
-}
-
-// static
-bool PrerenderManager::IsValidHttpMethod(const std::string& method) {
-  // method has been canonicalized to upper case at this point so we can just
-  // compare them.
-  DCHECK_EQ(method, StringToUpperASCII(method));
-  for (size_t i = 0; i < arraysize(kValidHttpMethods); ++i) {
-    if (method.compare(kValidHttpMethods[i]) == 0)
-      return true;
-  }
-
-  return false;
-}
-
 struct PrerenderManager::PrerenderContentsData {
   PrerenderContents* contents_;
   base::Time start_time_;
@@ -272,24 +226,6 @@ class PrerenderManager::MostVisitedSites
   std::set<GURL> urls_;
 };
 
-bool PrerenderManager::IsTopSite(const GURL& url) {
-  if (!most_visited_.get())
-    most_visited_.reset(new MostVisitedSites(profile_));
-  return most_visited_->IsTopSite(url);
-}
-
-bool PrerenderManager::IsPendingEntry(const GURL& url) const {
-  DCHECK(CalledOnValidThread());
-  for (std::list<PrerenderContentsData>::const_iterator it =
-           prerender_list_.begin();
-       it != prerender_list_.end();
-       ++it) {
-    if (it->contents_->IsPendingEntry(url))
-      return true;
-  }
-  return false;
-}
-
 PrerenderManager::PrerenderManager(Profile* profile,
                                    PrerenderTracker* prerender_tracker)
     : enabled_(true),
@@ -314,12 +250,6 @@ void PrerenderManager::Shutdown() {
   DoShutdown();
 }
 
-void PrerenderManager::SetPrerenderContentsFactory(
-    PrerenderContents::Factory* prerender_contents_factory) {
-  DCHECK(CalledOnValidThread());
-  prerender_contents_factory_.reset(prerender_contents_factory);
-}
-
 bool PrerenderManager::AddPrerenderFromLinkRelPrerender(
     int process_id,
     int route_id,
@@ -335,146 +265,12 @@ bool PrerenderManager::AddPrerenderFromLinkRelPrerender(
 bool PrerenderManager::AddPrerenderFromOmnibox(
     const GURL& url,
     SessionStorageNamespace* session_storage_namespace) {
-  DCHECK(session_storage_namespace);

[cbentzel, 2012/01/25 12:14:01]

Why was this removed?

   if (!IsOmniboxEnabled(profile_))
     return false;
   return AddPrerender(ORIGIN_OMNIBOX, std::make_pair(-1, -1), url,
                       content::Referrer(), session_storage_namespace);
 }
 
-bool PrerenderManager::AddPrerender(
-    Origin origin,
-    const std::pair<int, int>& child_route_id_pair,
-    const GURL& url_arg,
-    const content::Referrer& referrer,
-    SessionStorageNamespace* session_storage_namespace) {
-  DCHECK(CalledOnValidThread());
-
-  if (origin == ORIGIN_LINK_REL_PRERENDER &&
-      IsGoogleSearchResultURL(referrer.url)) {
-    origin = ORIGIN_GWS_PRERENDER;
-  }
-
-  // If the referring page is prerendering, defer the prerender.
-  std::list<PrerenderContentsData>::iterator source_prerender =
-      FindPrerenderContentsForChildRouteIdPair(child_route_id_pair);
-  if (source_prerender != prerender_list_.end()) {
-    source_prerender->contents_->AddPendingPrerender(
-        origin, url_arg, referrer);
-    return true;
-  }
-
-  DeleteOldEntries();
-  DeletePendingDeleteEntries();
-
-  GURL url = url_arg;
-  GURL alias_url;
-  if (IsControlGroup() && MaybeGetQueryStringBasedAliasURL(url, &alias_url))
-    url = alias_url;
-
-  // From here on, we will record a FinalStatus so we need to register with the
-  // histogram tracking.
-  histograms_->RecordPrerender(origin, url_arg);
-
-  uint8 experiment = GetQueryStringBasedExperiment(url_arg);
-
-  if (FindEntry(url)) {
-    RecordFinalStatus(origin, experiment, FINAL_STATUS_DUPLICATE);
-    return false;
-  }
-
-  // Do not prerender if there are too many render processes, and we would
-  // have to use an existing one.  We do not want prerendering to happen in
-  // a shared process, so that we can always reliably lower the CPU
-  // priority for prerendering.
-  // In single-process mode, ShouldTryToUseExistingProcessHost() always returns
-  // true, so that case needs to be explicitly checked for.
-  // TODO(tburkard): Figure out how to cancel prerendering in the opposite
-  // case, when a new tab is added to a process used for prerendering.
-  if (content::RenderProcessHost::ShouldTryToUseExistingProcessHost() &&
-      !content::RenderProcessHost::run_renderer_in_process()) {
-    RecordFinalStatus(origin, experiment, FINAL_STATUS_TOO_MANY_PROCESSES);
-    return false;
-  }
-
-  // Check if enough time has passed since the last prerender.
-  if (!DoesRateLimitAllowPrerender()) {
-    // Cancel the prerender. We could add it to the pending prerender list but
-    // this doesn't make sense as the next prerender request will be triggered
-    // by a navigation and is unlikely to be the same site.
-    RecordFinalStatus(origin, experiment, FINAL_STATUS_RATE_LIMIT_EXCEEDED);
-    return false;
-  }
-
-  RenderViewHost* source_render_view_host = NULL;
-  if (child_route_id_pair.first != -1) {
-    source_render_view_host =
-        RenderViewHost::FromID(child_route_id_pair.first,
-                               child_route_id_pair.second);
-    // Don't prerender page if parent RenderViewHost no longer exists, or it has
-    // no view.  The latter should only happen when the RenderView has closed.
-    if (!source_render_view_host || !source_render_view_host->view()) {
-      RecordFinalStatus(origin, experiment,
-                        FINAL_STATUS_SOURCE_RENDER_VIEW_CLOSED);
-      return false;
-    }
-  }
-
-  if (!session_storage_namespace && source_render_view_host) {
-    session_storage_namespace =
-        source_render_view_host->session_storage_namespace();
-  }
-
-  PrerenderContents* prerender_contents = CreatePrerenderContents(
-      url, referrer, origin, experiment);
-  if (!prerender_contents || !prerender_contents->Init())
-    return false;
-
-  histograms_->RecordPrerenderStarted(origin);
-
-  // TODO(cbentzel): Move invalid checks here instead of PrerenderContents?
-  PrerenderContentsData data(prerender_contents, GetCurrentTime());
-
-  prerender_list_.push_back(data);
-
-  if (IsControlGroup()) {
-    data.contents_->set_final_status(FINAL_STATUS_CONTROL_GROUP);
-  } else {
-    last_prerender_start_time_ = GetCurrentTimeTicks();
-    data.contents_->StartPrerendering(source_render_view_host,
-                                      session_storage_namespace);
-  }
-  while (prerender_list_.size() > config_.max_elements) {
-    data = prerender_list_.front();
-    prerender_list_.pop_front();
-    data.contents_->Destroy(FINAL_STATUS_EVICTED);
-  }
-  StartSchedulingPeriodicCleanups();
-  return true;
-}
-
-std::list<PrerenderManager::PrerenderContentsData>::iterator
-    PrerenderManager::FindPrerenderContentsForChildRouteIdPair(
-        const std::pair<int, int>& child_route_id_pair) {
-  std::list<PrerenderContentsData>::iterator it = prerender_list_.begin();
-  for (; it != prerender_list_.end(); ++it) {
-    PrerenderContents* prerender_contents = it->contents_;
-
-    int child_id;
-    int route_id;
-    bool has_child_id = prerender_contents->GetChildId(&child_id);
-    bool has_route_id = has_child_id &&
-                        prerender_contents->GetRouteId(&route_id);
-
-    if (has_child_id && has_route_id &&
-        child_id == child_route_id_pair.first &&
-        route_id == child_route_id_pair.second) {
-      break;
-    }
-  }
-  return it;
-}
-
 void PrerenderManager::DestroyPrerenderForRenderView(
     int process_id, int view_id, FinalStatus final_status) {
   DCHECK(CalledOnValidThread());
@@ -496,42 +292,14 @@ void PrerenderManager::CancelAllPrerenders() {
   }
 }
 
-void PrerenderManager::DeleteOldEntries() {
-  DCHECK(CalledOnValidThread());
-  while (!prerender_list_.empty()) {
-    PrerenderContentsData data = prerender_list_.front();
-    if (IsPrerenderElementFresh(data.start_time_))
-      return;
-    data.contents_->Destroy(FINAL_STATUS_TIMED_OUT);
-  }
-  MaybeStopSchedulingPeriodicCleanups();
-}
-
-PrerenderContents* PrerenderManager::GetEntryButNotSpecifiedWC(
-    const GURL& url,
-    WebContents* wc) {
+void PrerenderManager::CancelOmniboxPrerenders() {
   DCHECK(CalledOnValidThread());
-  DeleteOldEntries();
-  DeletePendingDeleteEntries();
   for (std::list<PrerenderContentsData>::iterator it = prerender_list_.begin();

[Peter Kasting, 2012/01/24 03:36:59]

Nit: I wonder if a typedef for this might be useful

-       it != prerender_list_.end();
-       ++it) {
-    PrerenderContents* prerender_contents = it->contents_;
-    if (prerender_contents->MatchesURL(url, NULL)) {
-      if (!prerender_contents->prerender_contents() ||
-          !wc ||
-          prerender_contents->prerender_contents()->web_contents() != wc) {
-        prerender_list_.erase(it);
-        return prerender_contents;
-      }
-    }
+       it != prerender_list_.end(); ) {
+    std::list<PrerenderContentsData>::iterator cur = it++;
+    if (cur->contents_->origin() == ORIGIN_OMNIBOX)
+      cur->contents_->Destroy(FINAL_STATUS_CANCELLED);
   }
-  // Entry not found.
-  return NULL;
-}
-
-PrerenderContents* PrerenderManager::GetEntry(const GURL& url) {
-  return GetEntryButNotSpecifiedWC(url, NULL);
 }
 
 bool PrerenderManager::MaybeUsePrerenderedPage(WebContents* web_contents,
@@ -741,52 +509,6 @@ void PrerenderManager::MoveEntryToPendingDelete(PrerenderContents* entry,
   PostCleanupTask();
 }
 
-base::Time PrerenderManager::GetCurrentTime() const {
-  return base::Time::Now();
-}
-
-base::TimeTicks PrerenderManager::GetCurrentTimeTicks() const {
-  return base::TimeTicks::Now();
-}
-
-bool PrerenderManager::IsPrerenderElementFresh(const base::Time start) const {
-  DCHECK(CalledOnValidThread());
-  base::Time now = GetCurrentTime();
-  return (now - start < config_.max_age);
-}
-
-PrerenderContents* PrerenderManager::CreatePrerenderContents(
-    const GURL& url,
-    const content::Referrer& referrer,
-    Origin origin,
-    uint8 experiment_id) {
-  DCHECK(CalledOnValidThread());
-  return prerender_contents_factory_->CreatePrerenderContents(
-      this, prerender_tracker_, profile_, url,
-      referrer, origin, experiment_id);
-}
-
-bool PrerenderManager::IsPendingDelete(PrerenderContents* entry) const {
-  DCHECK(CalledOnValidThread());
-  for (std::list<PrerenderContents*>::const_iterator it =
-          pending_delete_list_.begin();
-       it != pending_delete_list_.end();
-       ++it) {
-    if (*it == entry)
-      return true;
-  }
-
-  return false;
-}
-
-void PrerenderManager::DeletePendingDeleteEntries() {
-  while (!pending_delete_list_.empty()) {
-    PrerenderContents* contents = pending_delete_list_.front();
-    pending_delete_list_.pop_front();
-    delete contents;
-  }
-}
-
 // static
 void PrerenderManager::RecordPerceivedPageLoadTime(
     base::TimeDelta perceived_page_load_time,
@@ -828,108 +550,37 @@ void PrerenderManager::set_enabled(bool enabled) {
   enabled_ = enabled;
 }
 
-void PrerenderManager::AddCondition(const PrerenderCondition* condition) {
-  prerender_conditions_.push_back(condition);
-}
-
-PrerenderContents* PrerenderManager::FindEntry(const GURL& url) {
-  DCHECK(CalledOnValidThread());
-  for (std::list<PrerenderContentsData>::iterator it = prerender_list_.begin();
-       it != prerender_list_.end();
-       ++it) {
-    if (it->contents_->MatchesURL(url, NULL))
-      return it->contents_;
-  }
-  // Entry not found.
-  return NULL;
-}
-
-void PrerenderManager::DoShutdown() {
-  DestroyAllContents(FINAL_STATUS_MANAGER_SHUTDOWN);
-  STLDeleteElements(&prerender_conditions_);
-  profile_ = NULL;
-}
-
-bool PrerenderManager::DoesRateLimitAllowPrerender() const {
-  DCHECK(CalledOnValidThread());
-  base::TimeDelta elapsed_time =
-      GetCurrentTimeTicks() - last_prerender_start_time_;
-  histograms_->RecordTimeBetweenPrerenderRequests(elapsed_time);
-  if (!config_.rate_limit_enabled)
-    return true;
-  return elapsed_time >
-      base::TimeDelta::FromMilliseconds(kMinTimeBetweenPrerendersMs);
-}
-
-void PrerenderManager::StartSchedulingPeriodicCleanups() {
-  DCHECK(CalledOnValidThread());
-  if (repeating_timer_.IsRunning())
-    return;
-  repeating_timer_.Start(FROM_HERE,
-      base::TimeDelta::FromMilliseconds(kPeriodicCleanupIntervalMs),
-      this,
-      &PrerenderManager::PeriodicCleanup);
+// static
+PrerenderManager::PrerenderManagerMode PrerenderManager::GetMode() {
+  return mode_;
 }
 
-void PrerenderManager::MaybeStopSchedulingPeriodicCleanups() {
-  if (!prerender_list_.empty())
-    return;
-
-  DCHECK(CalledOnValidThread());
-  repeating_timer_.Stop();
+// static
+void PrerenderManager::SetMode(PrerenderManagerMode mode) {
+  mode_ = mode;
 }
 
-void PrerenderManager::DeleteOldTabContents() {
-  while (!old_tab_contents_list_.empty()) {
-    TabContentsWrapper* tab_contents = old_tab_contents_list_.front();
-    old_tab_contents_list_.pop_front();
-    // TODO(dominich): should we use Instant Unload Handler here?
-    delete tab_contents;
-  }
+// static
+bool PrerenderManager::IsPrerenderingPossible() {
+  return GetMode() == PRERENDER_MODE_ENABLED ||
+         GetMode() == PRERENDER_MODE_EXPERIMENT_PRERENDER_GROUP ||
+         GetMode() == PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP ||
+         GetMode() == PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP;
 }
 
-bool PrerenderManager::IsOldRenderViewHost(
-    const RenderViewHost* render_view_host) const {
-  for (std::list<TabContentsWrapper*>::const_iterator it =
-           old_tab_contents_list_.begin();
-       it != old_tab_contents_list_.end();
-       ++it) {
-    if ((*it)->web_contents()->GetRenderViewHost() == render_view_host)
-      return true;
-  }
-  return false;
+// static
+bool PrerenderManager::ActuallyPrerendering() {
+  return IsPrerenderingPossible() && !IsControlGroup();
 }
 
-void PrerenderManager::PeriodicCleanup() {
-  DCHECK(CalledOnValidThread());
-  DeleteOldTabContents();
-  DeleteOldEntries();
-
-  // Grab a copy of the current PrerenderContents pointers, so that we
-  // will not interfere with potential deletions of the list.
-  std::vector<PrerenderContents*> prerender_contents;
-  for (std::list<PrerenderContentsData>::iterator it = prerender_list_.begin();
-       it != prerender_list_.end();
-       ++it) {
-    DCHECK(it->contents_);
-    prerender_contents.push_back(it->contents_);
-  }
-  for (std::vector<PrerenderContents*>::iterator it =
-           prerender_contents.begin();
-       it != prerender_contents.end();
-       ++it) {
-    (*it)->DestroyWhenUsingTooManyResources();
-  }
-
-  DeletePendingDeleteEntries();
+// static
+bool PrerenderManager::IsControlGroup() {
+  return GetMode() == PRERENDER_MODE_EXPERIMENT_CONTROL_GROUP;
 }
 
-void PrerenderManager::PostCleanupTask() {
-  DCHECK(CalledOnValidThread());
-  MessageLoop::current()->PostTask(
-      FROM_HERE,
-      base::Bind(&PrerenderManager::PeriodicCleanup,
-                 weak_factory_.GetWeakPtr()));
+// static
+bool PrerenderManager::IsNoUseGroup() {
+  return GetMode() == PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP;
 }
 
 bool PrerenderManager::IsWebContentsPrerendering(
@@ -992,6 +643,18 @@ bool PrerenderManager::WouldWebContentsBePrerendered(
   return would_be_prerendered_tab_contents_set_.count(web_contents) > 0;
 }
 
+bool PrerenderManager::IsOldRenderViewHost(
+    const RenderViewHost* render_view_host) const {
+  for (std::list<TabContentsWrapper*>::const_iterator it =
+           old_tab_contents_list_.begin();
+       it != old_tab_contents_list_.end();
+       ++it) {
+    if ((*it)->web_contents()->GetRenderViewHost() == render_view_host)
+      return true;
+  }
+  return false;
+}
+
 bool PrerenderManager::HasRecentlyBeenNavigatedTo(const GURL& url) {
   DCHECK(CalledOnValidThread());
 
@@ -1006,33 +669,17 @@ bool PrerenderManager::HasRecentlyBeenNavigatedTo(const GURL& url) {
   return false;
 }
 
-void PrerenderManager::CleanUpOldNavigations() {
-  DCHECK(CalledOnValidThread());
-
-  // Cutoff.  Navigations before this cutoff can be discarded.
-  base::TimeTicks cutoff = GetCurrentTimeTicks() -
-      base::TimeDelta::FromMilliseconds(kNavigationRecordWindowMs);
-  while (!navigations_.empty()) {
-    if (navigations_.front().time_ > cutoff)
-      break;
-    navigations_.pop_front();
+// static
+bool PrerenderManager::IsValidHttpMethod(const std::string& method) {
+  // method has been canonicalized to upper case at this point so we can just
+  // compare them.
+  DCHECK_EQ(method, StringToUpperASCII(method));
+  for (size_t i = 0; i < arraysize(kValidHttpMethods); ++i) {
+    if (method.compare(kValidHttpMethods[i]) == 0)
+      return true;
   }
-}
-
-void PrerenderManager::ScheduleDeleteOldTabContents(
-    TabContentsWrapper* tab,
-    OnCloseTabContentsDeleter* deleter) {
-  old_tab_contents_list_.push_back(tab);
-  PostCleanupTask();
 
-  if (deleter) {
-    ScopedVector<OnCloseTabContentsDeleter>::iterator i = std::find(
-        on_close_tab_contents_deleters_.begin(),
-        on_close_tab_contents_deleters_.end(),
-        deleter);
-    DCHECK(i != on_close_tab_contents_deleters_.end());
-    on_close_tab_contents_deleters_.erase(i);
-  }
+  return false;
 }
 
 DictionaryValue* PrerenderManager::GetAsValue() const {
@@ -1060,49 +707,418 @@ void PrerenderManager::ClearData(int clear_flags) {
     prerender_history_->Clear();
 }
 
-void PrerenderManager::AddToHistory(PrerenderContents* contents) {
-  PrerenderHistory::Entry entry(contents->prerender_url(),
-                                contents->final_status(),
-                                contents->origin(),
-                                base::Time::Now());
-  prerender_history_->AddEntry(entry);
+void PrerenderManager::RecordFinalStatus(Origin origin,
+                                         uint8 experiment_id,
+                                         FinalStatus final_status) const {
+  histograms_->RecordFinalStatus(origin, experiment_id, final_status);
 }
 
-void PrerenderManager::RecordNavigation(const GURL& url) {
-  DCHECK(CalledOnValidThread());
+void PrerenderManager::AddCondition(const PrerenderCondition* condition) {
+  prerender_conditions_.push_back(condition);
+}
 
-  navigations_.push_back(NavigationRecord(url, GetCurrentTimeTicks()));
-  CleanUpOldNavigations();
+bool PrerenderManager::IsTopSite(const GURL& url) {
+  if (!most_visited_.get())
+    most_visited_.reset(new MostVisitedSites(profile_));
+  return most_visited_->IsTopSite(url);
 }
 
-Value* PrerenderManager::GetActivePrerendersAsValue() const {
-  ListValue* list_value = new ListValue();
+bool PrerenderManager::IsPendingEntry(const GURL& url) const {
+  DCHECK(CalledOnValidThread());
   for (std::list<PrerenderContentsData>::const_iterator it =
            prerender_list_.begin();
        it != prerender_list_.end();
        ++it) {
-    Value* prerender_value = it->contents_->GetAsValue();
-    if (!prerender_value)
-      continue;
-    list_value->Append(prerender_value);
+    if (it->contents_->IsPendingEntry(url))
+      return true;
   }
-  return list_value;
+  return false;
 }
 
-void PrerenderManager::DestroyAllContents(FinalStatus final_status) {
-  DeleteOldTabContents();
-  while (!prerender_list_.empty()) {
-    PrerenderContentsData data = prerender_list_.front();
-    prerender_list_.pop_front();
-    data.contents_->Destroy(final_status);
-  }
-  DeletePendingDeleteEntries();
+bool PrerenderManager::IsPrerendering(const GURL& url) {
+  DCHECK(CalledOnValidThread());
+  return (FindEntry(url) != NULL);
 }
 
-void PrerenderManager::RecordFinalStatus(Origin origin,
-                                         uint8 experiment_id,
-                                         FinalStatus final_status) const {
-  histograms_->RecordFinalStatus(origin, experiment_id, final_status);
+// protected
+void PrerenderManager::SetPrerenderContentsFactory(
+    PrerenderContents::Factory* prerender_contents_factory) {
+  DCHECK(CalledOnValidThread());
+  prerender_contents_factory_.reset(prerender_contents_factory);
+}
+
+void PrerenderManager::DoShutdown() {
+  DestroyAllContents(FINAL_STATUS_MANAGER_SHUTDOWN);
+  STLDeleteElements(&prerender_conditions_);
+  profile_ = NULL;
+}
+
+// private

[cbentzel, 2012/01/25 12:14:01]

Nit: I haven't really seen the // private comment in the code base. Not sure if
it needs to be introduced.

+bool PrerenderManager::AddPrerender(
+    Origin origin,
+    const std::pair<int, int>& child_route_id_pair,
+    const GURL& url_arg,
+    const content::Referrer& referrer,
+    SessionStorageNamespace* session_storage_namespace) {
+  DCHECK(CalledOnValidThread());
+
+  if (origin == ORIGIN_LINK_REL_PRERENDER &&
+      IsGoogleSearchResultURL(referrer.url)) {
+    origin = ORIGIN_GWS_PRERENDER;
+  }
+
+  // If the referring page is prerendering, defer the prerender.
+  std::list<PrerenderContentsData>::iterator source_prerender =
+      FindPrerenderContentsForChildRouteIdPair(child_route_id_pair);
+  if (source_prerender != prerender_list_.end()) {
+    source_prerender->contents_->AddPendingPrerender(
+        origin, url_arg, referrer);
+    return true;
+  }
+
+  DeleteOldEntries();
+  DeletePendingDeleteEntries();
+
+  GURL url = url_arg;
+  GURL alias_url;
+  if (IsControlGroup() && MaybeGetQueryStringBasedAliasURL(url, &alias_url))
+    url = alias_url;
+
+  // From here on, we will record a FinalStatus so we need to register with the
+  // histogram tracking.
+  histograms_->RecordPrerender(origin, url_arg);
+
+  uint8 experiment = GetQueryStringBasedExperiment(url_arg);
+
+  if (FindEntry(url)) {
+    RecordFinalStatus(origin, experiment, FINAL_STATUS_DUPLICATE);
+    return false;
+  }
+
+  // Do not prerender if there are too many render processes, and we would
+  // have to use an existing one.  We do not want prerendering to happen in
+  // a shared process, so that we can always reliably lower the CPU
+  // priority for prerendering.
+  // In single-process mode, ShouldTryToUseExistingProcessHost() always returns
+  // true, so that case needs to be explicitly checked for.
+  // TODO(tburkard): Figure out how to cancel prerendering in the opposite
+  // case, when a new tab is added to a process used for prerendering.
+  if (content::RenderProcessHost::ShouldTryToUseExistingProcessHost() &&
+      !content::RenderProcessHost::run_renderer_in_process()) {
+    RecordFinalStatus(origin, experiment, FINAL_STATUS_TOO_MANY_PROCESSES);
+    return false;
+  }
+
+  // Check if enough time has passed since the last prerender.
+  if (!DoesRateLimitAllowPrerender()) {
+    // Cancel the prerender. We could add it to the pending prerender list but
+    // this doesn't make sense as the next prerender request will be triggered
+    // by a navigation and is unlikely to be the same site.
+    RecordFinalStatus(origin, experiment, FINAL_STATUS_RATE_LIMIT_EXCEEDED);
+    return false;
+  }
+
+  RenderViewHost* source_render_view_host = NULL;
+  if (child_route_id_pair.first != -1) {
+    source_render_view_host =
+        RenderViewHost::FromID(child_route_id_pair.first,
+                               child_route_id_pair.second);
+    // Don't prerender page if parent RenderViewHost no longer exists, or it has
+    // no view.  The latter should only happen when the RenderView has closed.
+    if (!source_render_view_host || !source_render_view_host->view()) {
+      RecordFinalStatus(origin, experiment,
+                        FINAL_STATUS_SOURCE_RENDER_VIEW_CLOSED);
+      return false;
+    }
+  }
+
+  if (!session_storage_namespace && source_render_view_host) {
+    session_storage_namespace =
+        source_render_view_host->session_storage_namespace();
+  }
+
+  PrerenderContents* prerender_contents = CreatePrerenderContents(
+      url, referrer, origin, experiment);
+  if (!prerender_contents || !prerender_contents->Init())
+    return false;
+
+  histograms_->RecordPrerenderStarted(origin);
+
+  // TODO(cbentzel): Move invalid checks here instead of PrerenderContents?
+  PrerenderContentsData data(prerender_contents, GetCurrentTime());
+
+  prerender_list_.push_back(data);
+
+  if (IsControlGroup()) {
+    data.contents_->set_final_status(FINAL_STATUS_CONTROL_GROUP);
+  } else {
+    last_prerender_start_time_ = GetCurrentTimeTicks();
+    data.contents_->StartPrerendering(source_render_view_host,
+                                      session_storage_namespace);
+  }
+  while (prerender_list_.size() > config_.max_elements) {
+    data = prerender_list_.front();
+    prerender_list_.pop_front();
+    data.contents_->Destroy(FINAL_STATUS_EVICTED);
+  }
+  StartSchedulingPeriodicCleanups();
+  return true;
+}
+
+PrerenderContents* PrerenderManager::GetEntry(const GURL& url) {

[cbentzel, 2012/01/25 12:14:01]

I didn't check if all of the methods in this block are identical to what existed
before, assumed it was just a move in the file. 

+  return GetEntryButNotSpecifiedWC(url, NULL);
+}
+
+PrerenderContents* PrerenderManager::GetEntryButNotSpecifiedWC(
+    const GURL& url,
+    WebContents* wc) {
+  DCHECK(CalledOnValidThread());
+  DeleteOldEntries();
+  DeletePendingDeleteEntries();
+  for (std::list<PrerenderContentsData>::iterator it = prerender_list_.begin();
+       it != prerender_list_.end();
+       ++it) {
+    PrerenderContents* prerender_contents = it->contents_;
+    if (prerender_contents->MatchesURL(url, NULL)) {
+      if (!prerender_contents->prerender_contents() ||
+          !wc ||
+          prerender_contents->prerender_contents()->web_contents() != wc) {
+        prerender_list_.erase(it);
+        return prerender_contents;
+      }
+    }
+  }
+  // Entry not found.
+  return NULL;
+}
+
+void PrerenderManager::StartSchedulingPeriodicCleanups() {
+  DCHECK(CalledOnValidThread());
+  if (repeating_timer_.IsRunning())
+    return;
+  repeating_timer_.Start(FROM_HERE,
+      base::TimeDelta::FromMilliseconds(kPeriodicCleanupIntervalMs),
+      this,
+      &PrerenderManager::PeriodicCleanup);
+}
+
+void PrerenderManager::MaybeStopSchedulingPeriodicCleanups() {
+  if (!prerender_list_.empty())
+    return;
+
+  DCHECK(CalledOnValidThread());
+  repeating_timer_.Stop();
+}
+
+void PrerenderManager::PeriodicCleanup() {
+  DCHECK(CalledOnValidThread());
+  DeleteOldTabContents();
+  DeleteOldEntries();
+
+  // Grab a copy of the current PrerenderContents pointers, so that we
+  // will not interfere with potential deletions of the list.
+  std::vector<PrerenderContents*> prerender_contents;
+  for (std::list<PrerenderContentsData>::iterator it = prerender_list_.begin();
+       it != prerender_list_.end();
+       ++it) {
+    DCHECK(it->contents_);
+    prerender_contents.push_back(it->contents_);
+  }
+  for (std::vector<PrerenderContents*>::iterator it =
+           prerender_contents.begin();
+       it != prerender_contents.end();
+       ++it) {
+    (*it)->DestroyWhenUsingTooManyResources();
+  }
+
+  DeletePendingDeleteEntries();
+}
+
+void PrerenderManager::PostCleanupTask() {
+  DCHECK(CalledOnValidThread());
+  MessageLoop::current()->PostTask(
+      FROM_HERE,
+      base::Bind(&PrerenderManager::PeriodicCleanup,
+                 weak_factory_.GetWeakPtr()));
+}
+
+bool PrerenderManager::IsPrerenderElementFresh(const base::Time start) const {
+  DCHECK(CalledOnValidThread());
+  base::Time now = GetCurrentTime();
+  return (now - start < config_.max_age);
+}
+
+void PrerenderManager::DeleteOldEntries() {
+  DCHECK(CalledOnValidThread());
+  while (!prerender_list_.empty()) {
+    PrerenderContentsData data = prerender_list_.front();
+    if (IsPrerenderElementFresh(data.start_time_))
+      return;
+    data.contents_->Destroy(FINAL_STATUS_TIMED_OUT);
+  }
+  MaybeStopSchedulingPeriodicCleanups();
+}
+
+base::Time PrerenderManager::GetCurrentTime() const {
+  return base::Time::Now();
+}
+
+base::TimeTicks PrerenderManager::GetCurrentTimeTicks() const {
+  return base::TimeTicks::Now();
+}
+
+PrerenderContents* PrerenderManager::CreatePrerenderContents(
+    const GURL& url,
+    const content::Referrer& referrer,
+    Origin origin,
+    uint8 experiment_id) {
+  DCHECK(CalledOnValidThread());
+  return prerender_contents_factory_->CreatePrerenderContents(
+      this, prerender_tracker_, profile_, url,
+      referrer, origin, experiment_id);
+}
+
+bool PrerenderManager::IsPendingDelete(PrerenderContents* entry) const {
+  DCHECK(CalledOnValidThread());
+  for (std::list<PrerenderContents*>::const_iterator it =
+          pending_delete_list_.begin();
+       it != pending_delete_list_.end();
+       ++it) {
+    if (*it == entry)
+      return true;
+  }
+
+  return false;
+}
+
+void PrerenderManager::DeletePendingDeleteEntries() {
+  while (!pending_delete_list_.empty()) {
+    PrerenderContents* contents = pending_delete_list_.front();
+    pending_delete_list_.pop_front();
+    delete contents;
+  }
+}
+
+PrerenderContents* PrerenderManager::FindEntry(const GURL& url) {
+  DCHECK(CalledOnValidThread());
+  for (std::list<PrerenderContentsData>::iterator it = prerender_list_.begin();
+       it != prerender_list_.end();
+       ++it) {
+    if (it->contents_->MatchesURL(url, NULL))
+      return it->contents_;
+  }
+  // Entry not found.
+  return NULL;
+}
+
+std::list<PrerenderManager::PrerenderContentsData>::iterator
+    PrerenderManager::FindPrerenderContentsForChildRouteIdPair(
+        const std::pair<int, int>& child_route_id_pair) {
+  std::list<PrerenderContentsData>::iterator it = prerender_list_.begin();
+  for (; it != prerender_list_.end(); ++it) {
+    PrerenderContents* prerender_contents = it->contents_;
+
+    int child_id;
+    int route_id;
+    bool has_child_id = prerender_contents->GetChildId(&child_id);
+    bool has_route_id = has_child_id &&
+                        prerender_contents->GetRouteId(&route_id);
+
+    if (has_child_id && has_route_id &&
+        child_id == child_route_id_pair.first &&
+        route_id == child_route_id_pair.second) {
+      break;
+    }
+  }
+  return it;
+}
+
+bool PrerenderManager::DoesRateLimitAllowPrerender() const {
+  DCHECK(CalledOnValidThread());
+  base::TimeDelta elapsed_time =
+      GetCurrentTimeTicks() - last_prerender_start_time_;
+  histograms_->RecordTimeBetweenPrerenderRequests(elapsed_time);
+  if (!config_.rate_limit_enabled)
+    return true;
+  return elapsed_time >
+      base::TimeDelta::FromMilliseconds(kMinTimeBetweenPrerendersMs);
+}
+
+void PrerenderManager::DeleteOldTabContents() {
+  while (!old_tab_contents_list_.empty()) {
+    TabContentsWrapper* tab_contents = old_tab_contents_list_.front();
+    old_tab_contents_list_.pop_front();
+    // TODO(dominich): should we use Instant Unload Handler here?
+    delete tab_contents;
+  }
+}
+
+void PrerenderManager::CleanUpOldNavigations() {
+  DCHECK(CalledOnValidThread());
+
+  // Cutoff.  Navigations before this cutoff can be discarded.
+  base::TimeTicks cutoff = GetCurrentTimeTicks() -
+      base::TimeDelta::FromMilliseconds(kNavigationRecordWindowMs);
+  while (!navigations_.empty()) {
+    if (navigations_.front().time_ > cutoff)
+      break;
+    navigations_.pop_front();
+  }
+}
+
+void PrerenderManager::ScheduleDeleteOldTabContents(
+    TabContentsWrapper* tab,
+    OnCloseTabContentsDeleter* deleter) {
+  old_tab_contents_list_.push_back(tab);
+  PostCleanupTask();
+
+  if (deleter) {
+    ScopedVector<OnCloseTabContentsDeleter>::iterator i = std::find(
+        on_close_tab_contents_deleters_.begin(),
+        on_close_tab_contents_deleters_.end(),
+        deleter);
+    DCHECK(i != on_close_tab_contents_deleters_.end());
+    on_close_tab_contents_deleters_.erase(i);
+  }
+}
+
+void PrerenderManager::AddToHistory(PrerenderContents* contents) {
+  PrerenderHistory::Entry entry(contents->prerender_url(),
+                                contents->final_status(),
+                                contents->origin(),
+                                base::Time::Now());
+  prerender_history_->AddEntry(entry);
+}
+
+void PrerenderManager::RecordNavigation(const GURL& url) {
+  DCHECK(CalledOnValidThread());
+
+  navigations_.push_back(NavigationRecord(url, GetCurrentTimeTicks()));
+  CleanUpOldNavigations();
+}
+
+Value* PrerenderManager::GetActivePrerendersAsValue() const {
+  ListValue* list_value = new ListValue();
+  for (std::list<PrerenderContentsData>::const_iterator it =
+           prerender_list_.begin();
+       it != prerender_list_.end();
+       ++it) {
+    Value* prerender_value = it->contents_->GetAsValue();
+    if (!prerender_value)
+      continue;
+    list_value->Append(prerender_value);
+  }
+  return list_value;
+}
+
+void PrerenderManager::DestroyAllContents(FinalStatus final_status) {
+  DeleteOldTabContents();
+  while (!prerender_list_.empty()) {
+    PrerenderContentsData data = prerender_list_.front();
+    prerender_list_.pop_front();
+    data.contents_->Destroy(final_status);
+  }
+  DeletePendingDeleteEntries();
 }
 
 PrerenderManager* FindPrerenderManagerUsingRenderProcessId(