Handle interface to prerenders.

chrome/browser/prerender/prerender_manager.cc

 // Copyright (c) 2012 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/prerender/prerender_manager.h"
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
 #include "base/metrics/histogram.h"
 #include "base/stl_util.h"
 #include "base/time.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/cancelable_request.h"
 #include "chrome/browser/favicon/favicon_tab_helper.h"
 #include "chrome/browser/prerender/prerender_condition.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/prerender/prerender_field_trial.h"
 #include "chrome/browser/prerender/prerender_final_status.h"
+#include "chrome/browser/prerender/prerender_handle.h"
 #include "chrome/browser/prerender/prerender_histograms.h"
 #include "chrome/browser/prerender/prerender_history.h"
 #include "chrome/browser/prerender/prerender_local_predictor.h"
 #include "chrome/browser/prerender/prerender_manager_factory.h"
 #include "chrome/browser/prerender/prerender_tab_helper.h"
 #include "chrome/browser/prerender/prerender_tracker.h"
 #include "chrome/browser/prerender/prerender_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/tab_contents/core_tab_helper.h"
 #include "chrome/browser/ui/tab_contents/core_tab_helper_delegate.h"
@@ skipping 15 matching lines @@
 
 using content::BrowserThread;
 using content::RenderViewHost;
 using content::SessionStorageNamespace;
 using content::WebContents;
 
 namespace prerender {
 
 namespace {
 
-// Time window for which we will record windowed PLT's from the last
-// observed link rel=prefetch tag.
-const int kWindowDurationSeconds = 30;
-
-// Time interval at which periodic cleanups are performed.
-const int kPeriodicCleanupIntervalMs = 1000;
-
-// Time interval before a new prerender is allowed.
-const int kMinTimeBetweenPrerendersMs = 500;
-
-// Valid HTTP methods for prerendering.
-const char* const kValidHttpMethods[] = {
-  "GET",
-  "HEAD",
-  "OPTIONS",
-  "POST",
-  "TRACE",
-};
-
-// Length of prerender history, for display in chrome://net-internals
-const int kHistoryLength = 100;
-
 // Indicates whether a Prerender has been cancelled such that we need
 // a dummy replacement for the purpose of recording the correct PPLT for
 // the Match Complete case.
 // Traditionally, "Match" means that a prerendered page was actually visited &
 // the prerender was used.  Our goal is to have "Match" cases line up in the
 // control group & the experiment group, so that we can make meaningful
 // comparisons of improvements.  However, in the control group, since we don't
 // actually perform prerenders, many of the cancellation reasons cannot be
 // detected.  Therefore, in the Prerender group, when we cancel for one of these
 // reasons, we keep track of a dummy Prerender representing what we would
@@ skipping 12 matching lines @@
       final_status != FINAL_STATUS_APP_TERMINATING &&
       final_status != FINAL_STATUS_WINDOW_OPENER &&
       final_status != FINAL_STATUS_FRAGMENT_MISMATCH &&
       final_status != FINAL_STATUS_CACHE_OR_HISTORY_CLEARED &&
       final_status != FINAL_STATUS_CANCELLED &&
       final_status != FINAL_STATUS_SESSION_STORAGE_NAMESPACE_MISMATCH &&
       final_status != FINAL_STATUS_DEVTOOLS_ATTACHED &&
       final_status != FINAL_STATUS_CROSS_SITE_NAVIGATION_PENDING;
 }
 
+// Time window for which we will record windowed PLT's from the last
+// observed link rel=prefetch tag.
+const int kWindowDurationSeconds = 30;
+
+// Time interval at which periodic cleanups are performed.
+const int kPeriodicCleanupIntervalMs = 1000;
+
+// Time interval before a new prerender is allowed.
+const int kMinTimeBetweenPrerendersMs = 500;
+
+// Valid HTTP methods for prerendering.
+const char* const kValidHttpMethods[] = {
+  "GET",
+  "HEAD",
+  "OPTIONS",
+  "POST",
+  "TRACE",
+};
+
+// Length of prerender history, for display in chrome://net-internals
+const int kHistoryLength = 100;

[mmenke, 2012/06/22 16:12:45]

nit:  In cc files, the general style is to put constants first.  I assume this
is the opposite of h files because in h files the purpose is to emphasize
methods over variables, while in h files we want to emphasize constants, rather
than bury them.

(Know you don't like nits this early in the process, but this is a general
apparent Chrome consensus style, so thought I'd mention it.  It also decreases
the number of changes, which I find makes subsequent review passes a little
faster, but I'm slow.)

+
 }  // namespace
 
 class PrerenderManager::OnCloseTabContentsDeleter
     : public content::WebContentsDelegate,
       public base::SupportsWeakPtr<
           PrerenderManager::OnCloseTabContentsDeleter> {
  public:
   OnCloseTabContentsDeleter(PrerenderManager* manager,
                             TabContents* tab)
       : manager_(manager),
@@ skipping 37 matching lines @@
 // static
 bool PrerenderManager::is_prefetch_enabled_ = false;
 
 // static
 int PrerenderManager::prerenders_per_session_count_ = 0;
 
 // static
 PrerenderManager::PrerenderManagerMode PrerenderManager::mode_ =
     PRERENDER_MODE_ENABLED;
 
-struct PrerenderManager::PrerenderContentsData {
-  PrerenderContents* contents_;
-  base::Time start_time_;
-  int active_count_;
-  PrerenderContentsData(PrerenderContents* contents, base::Time start_time)
-      : contents_(contents),
-        start_time_(start_time),
-        active_count_(1) {
-    CHECK(contents);
-  }
-};
-
 struct PrerenderManager::NavigationRecord {
   GURL url_;
   base::TimeTicks time_;
   NavigationRecord(const GURL& url, base::TimeTicks time)
       : url_(url),
         time_(time) {
   }
 };
 
 PrerenderManager::PrerenderManager(Profile* profile,
@@ skipping 13 matching lines @@
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 }
 
 PrerenderManager::~PrerenderManager() {
 }
 
 void PrerenderManager::Shutdown() {
   DoShutdown();
 }
 
-bool PrerenderManager::AddPrerenderFromLinkRelPrerender(
+base::WeakPtr<PrerenderHandle> PrerenderManager::AddPrerenderFromLinkRelPrerender(
     int process_id,
     int route_id,
     const GURL& url,
     const content::Referrer& referrer,
     const gfx::Size& size) {
 #if defined(OS_ANDROID)
   // TODO(jcivelli): http://crbug.com/113322 We should have an option to disable
   //                link-prerender and enable omnibox-prerender only.
   return false;
 #else
-  std::pair<int, int> child_route_id_pair(process_id, route_id);
-  PrerenderContentsDataList::iterator it =
-      FindPrerenderContentsForChildRouteIdPair(child_route_id_pair);
-  if (it != prerender_list_.end()) {
+  if (PrerenderContents* parent_prerender_contents =
+          FindContentsForChildAndRoute(process_id, route_id)) {
     // Instead of prerendering from inside of a running prerender, we will defer
     // this request until its launcher is made visible.
-    it->contents_->AddPendingPrerender(url, referrer, size);
-    return true;
+    scoped_ptr<PrerenderHandle> scoped_prerender_handle(new PrerenderHandle);

[dominich, 2012/06/22 15:36:16]

Expected implementation:

return parent_prerender_contents->AddPendingPrerender(url, referrer, size);

where AddPendingPrerender creates and returns the PrerenderHandle.

+    base::WeakPtr<PrerenderHandle> prerender_handle =
+        scoped_prerender_handle.get()->AsWeakPtr();
+    parent_prerender_contents->AddPendingPrerender(
+        scoped_prerender_handle.Pass(), url, referrer, size);
+    return prerender_handle;
   }
 
   // Unit tests pass in a process_id == -1.
   RenderViewHost* source_render_view_host = NULL;
   SessionStorageNamespace* session_storage_namespace = NULL;
   if (process_id != -1) {
     source_render_view_host =
         RenderViewHost::FromID(process_id, route_id);
     if (!source_render_view_host || !source_render_view_host->GetView())
-      return false;
+      return base::WeakPtr<PrerenderHandle>();

[dominich, 2012/06/22 15:36:16]

return PrerenderHandle::kInvalidHandle;

where kInvalidHandle is a lazy static initialize PrerenderHandle marked as
invalid.

     session_storage_namespace =
         source_render_view_host->GetSessionStorageNamespace();
   }
 
   return AddPrerender(ORIGIN_LINK_REL_PRERENDER,
                       process_id, url, referrer, size,
-                      session_storage_namespace);
+                      session_storage_namespace,
+                      scoped_ptr<PrerenderHandle>());
 #endif
 }
 
-bool PrerenderManager::AddPrerenderFromOmnibox(
+base::WeakPtr<PrerenderHandle> PrerenderManager::AddPrerenderFromOmnibox(
     const GURL& url,
     SessionStorageNamespace* session_storage_namespace) {
   if (!IsOmniboxEnabled(profile_))
-    return false;
+    return base::WeakPtr<PrerenderHandle>();
   return AddPrerender(ORIGIN_OMNIBOX, -1, url,
                       content::Referrer(), gfx::Size(),
-                      session_storage_namespace);
+                      session_storage_namespace,
+                      scoped_ptr<PrerenderHandle>());
 }
 
-void PrerenderManager::MaybeCancelPrerender(const GURL& url) {
-  PrerenderContentsDataList::iterator it = FindPrerenderContentsForURL(url);
-  if (it == prerender_list_.end())
-    return;
-  PrerenderContentsData& prerender_contents_data = *it;
-  if (--prerender_contents_data.active_count_ == 0)
-    prerender_contents_data.contents_->Destroy(FINAL_STATUS_CANCELLED);
+void PrerenderManager::StartPendingPrerender(
+    scoped_ptr<PrerenderHandle> existing_prerender_handle,
+    int process_id,
+    const GURL& url,
+    const content::Referrer& referrer,
+    const gfx::Size& size,
+    content::SessionStorageNamespace* session_storage_namespace) {
+  DCHECK(existing_prerender_handle.get());
+  DCHECK(existing_prerender_handle->IsPending());
+  DCHECK(session_storage_namespace);
+  AddPrerender(ORIGIN_LINK_REL_PRERENDER,

[dominich, 2012/06/22 15:36:16]

origin should have been tracked. We might start pending prerenders from any
origin.

+               process_id, url, referrer, size, session_storage_namespace,
+               existing_prerender_handle.Pass());

[dominich, 2012/06/22 15:36:16]

ahah! Now I see the need for the existing prerender handle. Perhaps instead of
passing this through, it could be:

DCHECK(!existing_prerender_handle.is_valid());
existing_prerender_handle = AddPrerender(...);

existing_prerender_handle.Replace(AddPrerender(...));

which leaves the handle intact but replaces the contents.

 }
 
 void PrerenderManager::DestroyPrerenderForRenderView(
     int process_id, int view_id, FinalStatus final_status) {
   DCHECK(CalledOnValidThread());
-  PrerenderContentsDataList::iterator it =
-      FindPrerenderContentsForChildRouteIdPair(
-          std::make_pair(process_id, view_id));
-  if (it != prerender_list_.end()) {
-    PrerenderContents* prerender_contents = it->contents_;
+  if (PrerenderContents* prerender_contents =
+          FindContentsForChildAndRoute(process_id, view_id)) {
     prerender_contents->Destroy(final_status);
   }
 }
 
 void PrerenderManager::CancelAllPrerenders() {
   DCHECK(CalledOnValidThread());
-  while (!prerender_list_.empty()) {
-    PrerenderContentsData data = prerender_list_.front();
-    DCHECK(data.contents_);
-    data.contents_->Destroy(FINAL_STATUS_CANCELLED);
+  while (!prerender_map_.empty()) {
+    PrerenderContents* prerender_contents = prerender_map_.begin()->first;
+    DCHECK_EQ(prerender_contents, prerender_map_.begin()->second->contents());
+    prerender_contents->Destroy(FINAL_STATUS_CANCELLED);
   }
 }
 
-void PrerenderManager::CancelOmniboxPrerenders() {
-  DCHECK(CalledOnValidThread());
-  for (PrerenderContentsDataList::iterator it = prerender_list_.begin();
-       it != prerender_list_.end(); ) {
-    PrerenderContentsDataList::iterator cur = it++;
-    if (cur->contents_->origin() == ORIGIN_OMNIBOX)
-      cur->contents_->Destroy(FINAL_STATUS_CANCELLED);
-  }
-}
-
 bool PrerenderManager::MaybeUsePrerenderedPage(WebContents* web_contents,
                                                const GURL& url) {
   DCHECK(CalledOnValidThread());
   DCHECK(!IsWebContentsPrerendering(web_contents));
 
   scoped_ptr<PrerenderContents> prerender_contents(
       GetEntryButNotSpecifiedWC(url, web_contents));
   if (prerender_contents.get() == NULL)
     return false;
 
   // Do not use the prerendered version if there is an opener object.
   if (web_contents->HasOpener()) {
     prerender_contents.release()->Destroy(FINAL_STATUS_WINDOW_OPENER);
     return false;
   }
 
-  // Even if we match, the location.hash might be different. Record this as a

[dominich, 2012/06/22 15:36:16]

The problem with fragment mismatch is that we don't get the right fragment
passed through to us when starting a prerender (or at least we didn't...). Do we
now?

-  // separate final status.
-  GURL matching_url;
-  bool url_matches = prerender_contents->MatchesURL(url, &matching_url);
-  DCHECK(url_matches);
-  if (url_matches && url.ref() != matching_url.ref()) {
-    prerender_contents.release()->Destroy(FINAL_STATUS_FRAGMENT_MISMATCH);
-    return false;
-  }
-
   // If we are just in the control group (which can be detected by noticing
   // that prerendering hasn't even started yet), record that |web_contents| now
   // would be showing a prerendered contents, but otherwise, don't do anything.
   if (!prerender_contents->prerendering_has_started()) {
     MarkWebContentsAsWouldBePrerendered(web_contents);
     prerender_contents.release()->Destroy(FINAL_STATUS_WOULD_HAVE_BEEN_USED);
     return false;
   }
 
   // Don't use prerendered pages if debugger is attached to the tab.
   // See http://crbug.com/98541
   if (content::DevToolsAgentHostRegistry::IsDebuggerAttached(web_contents)) {
     DestroyAndMarkMatchCompleteAsUsed(prerender_contents.release(),
                                       FINAL_STATUS_DEVTOOLS_ATTACHED);
     return false;
   }
 
   // If the prerendered page is in the middle of a cross-site navigation,
   // don't swap it in because there isn't a good way to merge histories.
   if (prerender_contents->IsCrossSiteNavigationPending()) {
     DestroyAndMarkMatchCompleteAsUsed(
         prerender_contents.release(),
         FINAL_STATUS_CROSS_SITE_NAVIGATION_PENDING);
     return false;
   }
 
-  // If the session storage namespaces don't match, cancel the prerender.
-  RenderViewHost* old_render_view_host = web_contents->GetRenderViewHost();
-  RenderViewHost* new_render_view_host =
-      prerender_contents->prerender_contents()->web_contents()->
-          GetRenderViewHost();
-  DCHECK(old_render_view_host);
-  DCHECK(new_render_view_host);
-  if (old_render_view_host->GetSessionStorageNamespace() !=
-      new_render_view_host->GetSessionStorageNamespace()) {
-    DestroyAndMarkMatchCompleteAsUsed(
-        prerender_contents.release(),
-        FINAL_STATUS_SESSION_STORAGE_NAMESPACE_MISMATCH);
-    return false;
-  }
-
-  // If we don't want to use prerenders at all, we are done.
   // For bookkeeping purposes, we need to mark this WebContents to
   // reflect that it would have been prerendered.
   if (GetMode() == PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP) {
     MarkWebContentsAsWouldBePrerendered(web_contents);
     prerender_contents.release()->Destroy(FINAL_STATUS_WOULD_HAVE_BEEN_USED);
     return false;
   }
 
   int child_id, route_id;
   CHECK(prerender_contents->GetChildId(&child_id));
   CHECK(prerender_contents->GetRouteId(&route_id));
 
   // Try to set the prerendered page as used, so any subsequent attempts to
   // cancel on other threads will fail.  If this fails because the prerender
   // was already cancelled, possibly on another thread, fail.
   if (!prerender_tracker_->TryUse(child_id, route_id))
     return false;
 
   if (!prerender_contents->load_start_time().is_null()) {
     histograms_->RecordTimeUntilUsed(GetCurrentTimeTicks() -
                                      prerender_contents->load_start_time(),
                                      GetMaxAge());
   }
 
   histograms_->RecordPerSessionCount(++prerenders_per_session_count_);
   histograms_->RecordUsedPrerender(prerender_contents->origin());
   prerender_contents->set_final_status(FINAL_STATUS_USED);
 
+  RenderViewHost* new_render_view_host =
+      prerender_contents->prerender_contents()->web_contents()->GetRenderViewHost();
   new_render_view_host->Send(
       new PrerenderMsg_SetIsPrerendering(new_render_view_host->GetRoutingID(),
                                          false));
 
   TabContents* new_tab_contents =
       prerender_contents->ReleasePrerenderContents();
   TabContents* old_tab_contents = TabContents::FromWebContents(web_contents);
   DCHECK(new_tab_contents);
   DCHECK(old_tab_contents);
 
@@ skipping 46 matching lines @@
 }
 
 void PrerenderManager::MoveEntryToPendingDelete(PrerenderContents* entry,
                                                 FinalStatus final_status) {
   DCHECK(CalledOnValidThread());
   DCHECK(entry);
   // Confirm this entry has not already been moved to the pending delete list.
   DCHECK_EQ(0, std::count(pending_delete_list_.begin(),
                           pending_delete_list_.end(), entry));
 
-  for (PrerenderContentsDataList::iterator it = prerender_list_.begin();
-       it != prerender_list_.end();
-       ++it) {
-    if (it->contents_ == entry) {
-      bool swapped_in_dummy_replacement = false;
+  PrerenderHandleMap::iterator it = prerender_map_.find(entry);
+  if (it == prerender_map_.end())
+    return;
 
-      // If this PrerenderContents is being deleted due to a cancellation,
-      // we need to create a dummy replacement for PPLT accounting purposes
-      // for the Match Complete group.
-      // This is the case if the cancellation is for any reason that would not
-      // occur in the control group case.
-      if (entry->match_complete_status() ==
-          PrerenderContents::MATCH_COMPLETE_DEFAULT &&
-          NeedMatchCompleteDummyForFinalStatus(final_status) &&
-          ActuallyPrerendering()) {
-        // TODO(tburkard): I'd like to DCHECK that we are actually prerendering.
-        // However, what if new conditions are added and
-        // NeedMatchCompleteDummyForFinalStatus, is not being updated.  Not sure
-        // what's the best thing to do here.  For now, I will just check whether
-        // we are actually prerendering.
-        entry->set_match_complete_status(
-            PrerenderContents::MATCH_COMPLETE_REPLACED);
-        if (PrerenderContents* dummy_replacement_prerender_contents =
-                CreatePrerenderContents(entry->prerender_url(),
-                                        entry->referrer(),
-                                        entry->origin(),
-                                        entry->experiment_id())) {
-          dummy_replacement_prerender_contents->set_match_complete_status(
-              PrerenderContents::MATCH_COMPLETE_REPLACEMENT_PENDING);
-          if (!dummy_replacement_prerender_contents->Init())
-            break;
-          dummy_replacement_prerender_contents->
-              AddAliasURLsFromOtherPrerenderContents(entry);
-          dummy_replacement_prerender_contents->set_match_complete_status(
-              PrerenderContents::MATCH_COMPLETE_REPLACEMENT);
-          it->contents_ = dummy_replacement_prerender_contents;
-          swapped_in_dummy_replacement = true;
-        }
-      }
-      if (!swapped_in_dummy_replacement)
-        prerender_list_.erase(it);
-      break;
-    }
+  // If this PrerenderContents is being deleted due to a cancellation,
+  // we need to create a dummy replacement for PPLT accounting purposes
+  // for the Match Complete group.
+  // This is the case if the cancellation is for any reason that would not
+  // occur in the control group case.
+  if (entry->match_complete_status() ==
+      PrerenderContents::MATCH_COMPLETE_DEFAULT &&
+      NeedMatchCompleteDummyForFinalStatus(final_status) &&
+      ActuallyPrerendering()) {
+    // TODO(tburkard): I'd like to DCHECK that we are actually prerendering.
+    // However, what if new conditions are added and
+    // NeedMatchCompleteDummyForFinalStatus, is not being updated.  Not sure
+    // what's the best thing to do here.  For now, I will just check whether
+    // we are actually prerendering.
+    entry->set_match_complete_status(
+        PrerenderContents::MATCH_COMPLETE_REPLACED);
+    PrerenderContents*
+        dummy_replacement_prerender_contents = entry->CreateDummyReplacement();
+    DCHECK(dummy_replacement_prerender_contents);
+
+    dummy_replacement_prerender_contents->set_match_complete_status(
+        PrerenderContents::MATCH_COMPLETE_REPLACEMENT_PENDING);
+    DCHECK(dummy_replacement_prerender_contents->Init());
+    dummy_replacement_prerender_contents->
+        AddAliasURLsFromOtherPrerenderContents(entry);
+    dummy_replacement_prerender_contents->set_match_complete_status(
+        PrerenderContents::MATCH_COMPLETE_REPLACEMENT);
+    prerender_map_.insert(std::make_pair(dummy_replacement_prerender_contents,
+                                         it->second));
   }
+  prerender_map_.erase(it);
+
   AddToHistory(entry);
   pending_delete_list_.push_back(entry);
 
   // Destroy the old WebContents relatively promptly to reduce resource usage,
   // and in the case of HTML5 media, reduce the change of playing any sound.
   PostCleanupTask();
 }
 
 // static
 void PrerenderManager::RecordPerceivedPageLoadTime(
@@ skipping 90 matching lines @@
 }
 
 // static
 bool PrerenderManager::IsNoUseGroup() {
   return GetMode() == PRERENDER_MODE_EXPERIMENT_NO_USE_GROUP;
 }
 
 bool PrerenderManager::IsWebContentsPrerendering(
     WebContents* web_contents) const {
   DCHECK(CalledOnValidThread());
-  for (PrerenderContentsDataList::const_iterator it = prerender_list_.begin();
-       it != prerender_list_.end();
+  for (PrerenderHandleMap::const_iterator it = prerender_map_.begin();
+       it != prerender_map_.end();
        ++it) {
-    TabContents* prerender_tab_contents = it->contents_->prerender_contents();
+    TabContents* prerender_tab_contents = it->first->prerender_contents();
     if (prerender_tab_contents &&
         prerender_tab_contents->web_contents() == web_contents) {
       return true;
     }
   }
 
   // Also look through the pending-deletion list.
   for (std::list<PrerenderContents*>::const_iterator it =
            pending_delete_list_.begin();
        it != pending_delete_list_.end();
        ++it) {
     TabContents* prerender_tab_contents = (*it)->prerender_contents();
     if (prerender_tab_contents &&
         prerender_tab_contents->web_contents() == web_contents)
       return true;
   }
 
   return false;
 }
 
-bool PrerenderManager::DidPrerenderFinishLoading(const GURL& url) const {
-  DCHECK(CalledOnValidThread());
-  PrerenderContents* contents = FindEntry(url);
-  return contents ? contents->has_finished_loading() : false;
-}
-
 void PrerenderManager::MarkWebContentsAsPrerendered(WebContents* web_contents) {
   DCHECK(CalledOnValidThread());
   prerendered_tab_contents_set_.insert(web_contents);
 }
 
 void PrerenderManager::MarkWebContentsAsWouldBePrerendered(
     WebContents* web_contents) {
   DCHECK(CalledOnValidThread());
   would_be_prerendered_map_[web_contents] = true;
 }
@@ skipping 95 matching lines @@
   histograms_->RecordFinalStatus(origin,
                                  experiment_id,
                                  mc_status,
                                  final_status);
 }
 
 void PrerenderManager::AddCondition(const PrerenderCondition* condition) {
   prerender_conditions_.push_back(condition);
 }
 
-bool PrerenderManager::IsPendingEntry(const GURL& url) const {
-  DCHECK(CalledOnValidThread());
-  for (PrerenderContentsDataList::const_iterator it = prerender_list_.begin();
-       it != prerender_list_.end();
-       ++it) {
-    if (it->contents_->IsPendingEntry(url))
-      return true;
-  }
-  return false;
-}
-
-bool PrerenderManager::IsPrerendering(const GURL& url) const {
-  DCHECK(CalledOnValidThread());
-  return (FindEntry(url) != NULL);
-}
-
 void PrerenderManager::RecordNavigation(const GURL& url) {
   DCHECK(CalledOnValidThread());
 
   navigations_.push_back(NavigationRecord(url, GetCurrentTimeTicks()));
   CleanUpOldNavigations();
 }
 
 // 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_);
   on_close_tab_contents_deleters_.reset();
   profile_ = NULL;
 }
 
+PrerenderContents* PrerenderManager::FindEntry(
+    const GURL& url) {
+  if (PrerenderHandle* handle = FindHandle(url, NULL))
+    return handle->contents();
+  return NULL;
+}
+
 // private
-bool PrerenderManager::AddPrerender(
+base::WeakPtr<PrerenderHandle> PrerenderManager::AddPrerender(
     Origin origin,
     int process_id,
     const GURL& url_arg,
     const content::Referrer& referrer,
     const gfx::Size& size,
-    SessionStorageNamespace* session_storage_namespace) {
+    SessionStorageNamespace* session_storage_namespace,
+    scoped_ptr<PrerenderHandle> preexisting_prerender_handle) {
   DCHECK(CalledOnValidThread());
 
+  // Take ownership of preeexisting_prerender_handle immediately if it was
+  // provided, otherwise create a new PrerenderHandle to own so we don't have
+  // special cases for early exits depending on if preexisting_prerender_handle
+  // was provided.
+  scoped_ptr<PrerenderHandle>
+      scoped_prerender_handle = preexisting_prerender_handle.Pass();
+  if (!scoped_prerender_handle.get())
+    scoped_prerender_handle.reset(new PrerenderHandle);
+  DCHECK(!scoped_prerender_handle->contents());
+  base::WeakPtr<PrerenderHandle> prerender_handle =
+      scoped_prerender_handle->AsWeakPtr();
+
   if (!IsEnabled())
-    return false;
+    return base::WeakPtr<PrerenderHandle>();
 
   if (origin == ORIGIN_LINK_REL_PRERENDER &&
       IsGoogleSearchResultURL(referrer.url)) {
     origin = ORIGIN_GWS_PRERENDER;
   }
 
   DeleteOldEntries();
   DeletePendingDeleteEntries();
 
   GURL url = url_arg;
   GURL alias_url;
   uint8 experiment = GetQueryStringBasedExperiment(url_arg);
   bool control_group_behavior =
       IsControlGroup() || IsControlGroupExperiment(experiment);
   if (control_group_behavior &&
       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);
 
-  if (PrerenderContentsData* prerender_contents_data = FindEntryData(url)) {
-    ++prerender_contents_data->active_count_;
+  if (PrerenderHandle* preexisting_prerender_handle =
+          FindHandle(url, session_storage_namespace)) {
     RecordFinalStatus(origin, experiment, FINAL_STATUS_DUPLICATE);
-    return true;
+    preexisting_prerender_handle->AddDuplicate(scoped_prerender_handle.Pass());
+    return prerender_handle;
   }
 
   // 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.
   // On Android we do reuse processes as we have a limited number of them and we
   // still want the benefits of prerendering even when several tabs are open.
 #if !defined(OS_ANDROID)
   if (content::RenderProcessHost::ShouldTryToUseExistingProcessHost(
           profile_, url) &&
       !content::RenderProcessHost::run_renderer_in_process()) {
     RecordFinalStatus(origin, experiment, FINAL_STATUS_TOO_MANY_PROCESSES);
-    return false;
+    // TODO: duplicates holding zone?
+    return base::WeakPtr<PrerenderHandle>();
   }
 #endif
 
   // 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;
+    return base::WeakPtr<PrerenderHandle>();
   }
 
   PrerenderContents* prerender_contents = CreatePrerenderContents(
       url, referrer, origin, experiment);
   if (!prerender_contents || !prerender_contents->Init())
-    return false;
-
+    return base::WeakPtr<PrerenderHandle>();
+  
   histograms_->RecordPrerenderStarted(origin);
-
+  
   // TODO(cbentzel): Move invalid checks here instead of PrerenderContents?
-  PrerenderContentsData data(prerender_contents, GetCurrentTime());
-
-  prerender_list_.push_back(data);
+  scoped_prerender_handle->SetContents(prerender_contents);
+  prerender_map_.insert(
+      std::make_pair(prerender_contents,
+                     make_linked_ptr(scoped_prerender_handle.release())));
 
   last_prerender_start_time_ = GetCurrentTimeTicks();
 
-  data.contents_->StartPrerendering(process_id, size, session_storage_namespace,
-                                    control_group_behavior);
+  prerender_contents->StartPrerendering(process_id, size, session_storage_namespace,
+                                        control_group_behavior);
 
-  while (prerender_list_.size() > config_.max_elements) {
-    data = prerender_list_.front();
-    prerender_list_.pop_front();
-    data.contents_->Destroy(FINAL_STATUS_EVICTED);
+  while (prerender_map_.size() > config_.max_elements) {
+    prerender_contents = prerender_map_.begin()->first;
+    DCHECK(prerender_contents);
+    const size_t old_size = prerender_map_.size();
+    prerender_contents->Destroy(FINAL_STATUS_EVICTED);
+    DCHECK_GT(old_size, prerender_map_.size());
   }
+
   StartSchedulingPeriodicCleanups();
-  return true;
+  return prerender_handle;
 }
 
 PrerenderContents* PrerenderManager::GetEntry(const GURL& url) {
   return GetEntryButNotSpecifiedWC(url, NULL);
 }
 
 PrerenderContents* PrerenderManager::GetEntryButNotSpecifiedWC(
     const GURL& url,
-    WebContents* wc) {
+    WebContents* web_contents) {
   DCHECK(CalledOnValidThread());
   DeleteOldEntries();
   DeletePendingDeleteEntries();
-  for (PrerenderContentsDataList::iterator it = prerender_list_.begin();
-       it != prerender_list_.end();
+
+  SessionStorageNamespace* session_storage_namespace = NULL;
+  if (web_contents) {
+    DCHECK(web_contents->GetRenderViewHost());
+    session_storage_namespace =
+        web_contents->GetRenderViewHost()->GetSessionStorageNamespace();
+    DCHECK(session_storage_namespace);
+  }
+
+  for (PrerenderHandleMap::iterator it = prerender_map_.begin();
+       it != prerender_map_.end();
        ++it) {
-    PrerenderContents* prerender_contents = it->contents_;
-    if (prerender_contents->MatchesURL(url, NULL) &&
-        !IsNoSwapInExperiment(prerender_contents->experiment_id())) {
-      if (!prerender_contents->prerender_contents() ||
-          !wc ||
-          prerender_contents->prerender_contents()->web_contents() != wc) {
-        prerender_list_.erase(it);
-        return prerender_contents;
-      }
+    PrerenderContents* prerender_contents = it->first;
+    if (!prerender_contents->Matches(url, session_storage_namespace) ||
+        IsNoSwapInExperiment(prerender_contents->experiment_id())) {
+      break;
+    }
+
+    TabContents* tab_contents = prerender_contents->prerender_contents();
+    if (!tab_contents || !web_contents ||
+        tab_contents->web_contents() != web_contents) {
+      PrerenderHandle* prerender_handle = it->second.get();
+      prerender_handle->SetContents(NULL);
+      prerender_map_.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;
-
+void PrerenderManager::StopSchedulingPeriodicCleanups() {
   DCHECK(CalledOnValidThread());
   repeating_timer_.Stop();
 }
 
 void PrerenderManager::PeriodicCleanup() {
   DCHECK(CalledOnValidThread());
   DeleteOldTabContents();
   DeleteOldEntries();
+  if (prerender_map_.empty())
+    StopSchedulingPeriodicCleanups();
 
   // 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 (PrerenderContentsDataList::iterator it = prerender_list_.begin();
-       it != prerender_list_.end();
+  for (PrerenderHandleMap::iterator it = prerender_map_.begin();
+       it != prerender_map_.end();
        ++it) {
-    DCHECK(it->contents_);
-    prerender_contents.push_back(it->contents_);
+    DCHECK(it->first);
+    prerender_contents.push_back(it->first);
   }
   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()));
 }
 
 base::TimeDelta PrerenderManager::GetMaxAge() const {
   return (GetMode() == PRERENDER_MODE_EXPERIMENT_5MIN_TTL_GROUP ?
       base::TimeDelta::FromSeconds(300) : config_.max_age);
 }
 
-bool PrerenderManager::IsPrerenderElementFresh(const base::Time start) const {
+bool PrerenderManager::IsPrerenderFresh(base::TimeTicks start) const {
   DCHECK(CalledOnValidThread());
-  base::Time now = GetCurrentTime();
-  return (now - start < GetMaxAge());
+  base::TimeTicks now = GetCurrentTimeTicks();
+  return now - start < GetMaxAge();
 }
 
 void PrerenderManager::DeleteOldEntries() {
   DCHECK(CalledOnValidThread());
-  while (!prerender_list_.empty()) {
-    PrerenderContentsData data = prerender_list_.front();
-    if (IsPrerenderElementFresh(data.start_time_))
+
+  while (!prerender_map_.empty()) {
+    PrerenderContents* contents = prerender_map_.begin()->first;
+    DCHECK(contents);
+    if (IsPrerenderFresh(contents->load_start_time()))
       return;
-    data.contents_->Destroy(FINAL_STATUS_TIMED_OUT);
+    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);
 }
 
 void PrerenderManager::DeletePendingDeleteEntries() {
   while (!pending_delete_list_.empty()) {
     PrerenderContents* contents = pending_delete_list_.front();
     pending_delete_list_.pop_front();
     delete contents;
   }
 }
 
-PrerenderManager::PrerenderContentsData* PrerenderManager::FindEntryData(
-    const GURL& url) {
-  DCHECK(CalledOnValidThread());
-  PrerenderContentsDataList::iterator it = FindPrerenderContentsForURL(url);
-  if (it == prerender_list_.end())
-    return NULL;
-  PrerenderContentsData& prerender_contents_data = *it;
-  return &prerender_contents_data;
-}
-
-PrerenderContents* PrerenderManager::FindEntry(const GURL& url) const {
-  DCHECK(CalledOnValidThread());
-  for (PrerenderContentsDataList::const_iterator it = prerender_list_.begin();
-       it != prerender_list_.end();
+PrerenderHandle* PrerenderManager::FindHandle(
+    const GURL& url,
+    const SessionStorageNamespace* session_storage_namespace) {
+  for (PrerenderHandleMap::iterator it = prerender_map_.begin();
+       it != prerender_map_.end();
        ++it) {
-    if (it->contents_->MatchesURL(url, NULL))
-      return it->contents_;
+    PrerenderContents* prerender_contents = it->first;
+    if (prerender_contents->Matches(url, session_storage_namespace))
+      return it->second.get();
   }
-  // Entry not found.
   return NULL;
 }
 
-PrerenderManager::PrerenderContentsDataList::iterator
-    PrerenderManager::FindPrerenderContentsForChildRouteIdPair(
-        const std::pair<int, int>& child_route_id_pair) {
-  PrerenderContentsDataList::iterator it = prerender_list_.begin();
-  for (; it != prerender_list_.end(); ++it) {
-    PrerenderContents* prerender_contents = it->contents_;
+PrerenderContents* PrerenderManager::FindContentsForChildAndRoute(
+    const int child_id, const int route_id) {
+  PrerenderHandleMap::iterator it = prerender_map_.begin();
+  for (; it != prerender_map_.end(); ++it) {
+    PrerenderContents* prerender_contents = it->first;
 
-    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);
+    int contents_child_id;
+    if (!prerender_contents->GetChildId(&contents_child_id))
+      continue;
+    int contents_route_id;
+    if (!prerender_contents->GetRouteId(&contents_route_id))
+      continue;
 
-    if (has_child_id && has_route_id &&
-        child_id == child_route_id_pair.first &&
-        route_id == child_route_id_pair.second) {
-      break;
-    }
+    if (contents_child_id == child_id && contents_route_id == route_id)
+      return it->first;
   }
-  return it;
-}
-
-PrerenderManager::PrerenderContentsDataList::iterator
-    PrerenderManager::FindPrerenderContentsForURL(const GURL& url) {
-  for (PrerenderContentsDataList::iterator it = prerender_list_.begin();
-       it != prerender_list_.end(); ++it) {
-    if (it->contents_->MatchesURL(url, NULL))
-      return it;
-  }
-  return prerender_list_.end();
+  return 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 >
@@ skipping 41 matching lines @@
 void PrerenderManager::AddToHistory(PrerenderContents* contents) {
   PrerenderHistory::Entry entry(contents->prerender_url(),
                                 contents->final_status(),
                                 contents->origin(),
                                 base::Time::Now());
   prerender_history_->AddEntry(entry);
 }
 
 Value* PrerenderManager::GetActivePrerendersAsValue() const {
   ListValue* list_value = new ListValue();
-  for (PrerenderContentsDataList::const_iterator it = prerender_list_.begin();
-       it != prerender_list_.end();
+  for (PrerenderHandleMap::const_iterator it = prerender_map_.begin();
+       it != prerender_map_.end();
        ++it) {
-    Value* prerender_value = it->contents_->GetAsValue();
-    if (!prerender_value)
-      continue;
-    list_value->Append(prerender_value);
+    Value* prerender_value = it->first->GetAsValue();
+    if (prerender_value)
+      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);
+  while (!prerender_map_.empty()) {
+    PrerenderContents* contents = prerender_map_.begin()->first;
+    const size_t old_size = prerender_map_.size();
+    contents->Destroy(final_status);
+    DCHECK_GT(old_size, prerender_map_.size());
   }
   DeletePendingDeleteEntries();
 }
 
 void PrerenderManager::DestroyAndMarkMatchCompleteAsUsed(
     PrerenderContents* prerender_contents,
     FinalStatus final_status) {
   prerender_contents->set_match_complete_status(
       PrerenderContents::MATCH_COMPLETE_REPLACED);
   histograms_->RecordFinalStatus(prerender_contents->origin(),
@@ skipping 38 matching lines @@
   if (!render_process_host || !render_process_host->GetBrowserContext())
     return NULL;
   Profile* profile = Profile::FromBrowserContext(
       render_process_host->GetBrowserContext());
   if (!profile)
     return NULL;
   return PrerenderManagerFactory::GetInstance()->GetForProfile(profile);
 }
 
 }  // namespace prerender