Add <link rel=next> support to prerender.

chrome/browser/prerender/prerender_link_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_link_manager.h"
 
 #include <functional>
 #include <limits>
 #include <set>
+#include <string>
 #include <utility>
 
 #include "base/memory/scoped_ptr.h"
+#include "base/metrics/field_trial.h"
 #include "chrome/browser/prerender/prerender_contents.h"
 #include "chrome/browser/prerender/prerender_handle.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/prerender/prerender_manager_factory.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/prerender_messages.h"
+#include "chrome/common/prerender_types.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_view_host.h"
 #include "content/public/browser/session_storage_namespace.h"
 #include "content/public/common/referrer.h"
 #include "ui/gfx/size.h"
 #include "url/gurl.h"
 
 using base::TimeDelta;
 using base::TimeTicks;
 using content::RenderViewHost;
 using content::SessionStorageNamespace;
 
+namespace prerender {
+
 namespace {
 
+bool ShouldStartRelNextPrerenders() {
+  const std::string experiment_name =
+      base::FieldTrialList::FindFullName("PrerenderRelNextTrial");
+
+  return experiment_name.find("Yes") != std::string::npos;
+}
+
+bool ShouldStartPrerender(uint32 rel_types) {
+  const bool should_start_rel_next_prerenders =
+      ShouldStartRelNextPrerenders();
+
+  if (rel_types & PrerenderRelTypePrerender) {
+    return true;
+  } else if (should_start_rel_next_prerenders &&
+             (rel_types & PrerenderRelTypeNext) == PrerenderRelTypeNext) {
+    return true;
+  }
+  return false;
+}
+
 void Send(int child_id, IPC::Message* raw_message) {
   using content::RenderProcessHost;
   scoped_ptr<IPC::Message> own_message(raw_message);
 
   RenderProcessHost* render_process_host = RenderProcessHost::FromID(child_id);
   if (!render_process_host)
     return;
   render_process_host->Send(own_message.release());
 }
 
 }  // namespace
 
-namespace prerender {
-
 // Helper class to implement PrerenderContents::Observer and watch prerenders
 // which launch other prerenders.
 class PrerenderLinkManager::PendingPrerenderManager
     : public PrerenderContents::Observer {
  public:
   explicit PendingPrerenderManager(PrerenderLinkManager* link_manager)
       : link_manager_(link_manager) {}
 
   virtual ~PendingPrerenderManager() {
     DCHECK(observed_launchers_.empty());
@@ skipping 45 matching lines @@
           << "PrerenderManager.";
       delete i->handle;
       i->handle = 0;
     }
   }
 }
 
 void PrerenderLinkManager::OnAddPrerender(int launcher_child_id,
                                           int prerender_id,
                                           const GURL& url,
+                                          uint32 rel_types,
                                           const content::Referrer& referrer,
                                           const gfx::Size& size,
                                           int render_view_route_id) {
   DCHECK_EQ(static_cast<LinkPrerender*>(NULL),
             FindByLauncherChildIdAndPrerenderId(launcher_child_id,
                                                 prerender_id));
   content::RenderProcessHost* rph =
       content::RenderProcessHost::FromID(launcher_child_id);
   // Guests inside <webview> do not support cross-process navigation and so we
   // do not allow guests to prerender content.
   if (rph && rph->IsGuest())
     return;
 
   // Check if the launcher is itself an unswapped prerender.
   PrerenderContents* prerender_contents =
       manager_->GetPrerenderContentsForRoute(launcher_child_id,
                                              render_view_route_id);
   if (prerender_contents &&
       prerender_contents->final_status() != FINAL_STATUS_MAX) {
     // The launcher is a prerender about to be destroyed asynchronously, but
     // its AddLinkRelPrerender message raced with shutdown. Ignore it.
     DCHECK_NE(FINAL_STATUS_USED, prerender_contents->final_status());
     return;
   }
 
   LinkPrerender
-      prerender(launcher_child_id, prerender_id, url, referrer, size,
+      prerender(launcher_child_id, prerender_id, url, rel_types, referrer, size,
                 render_view_route_id, manager_->GetCurrentTimeTicks(),
                 prerender_contents);
   prerenders_.push_back(prerender);
   if (prerender_contents)
     pending_prerender_manager_->ObserveLauncher(prerender_contents);
   else
     StartPrerenders();
 }
 
 void PrerenderLinkManager::OnCancelPrerender(int child_id, int prerender_id) {
@@ skipping 40 matching lines @@
     const size_t running_prerender_count = CountRunningPrerenders();
     OnAbandonPrerender(child_id, it->prerender_id);
     DCHECK_EQ(running_prerender_count, CountRunningPrerenders());
   }
 }
 
 PrerenderLinkManager::LinkPrerender::LinkPrerender(
     int launcher_child_id,
     int prerender_id,
     const GURL& url,
+    uint32 rel_types,
     const content::Referrer& referrer,
     const gfx::Size& size,
     int render_view_route_id,
     TimeTicks creation_time,
     PrerenderContents* deferred_launcher)
     : launcher_child_id(launcher_child_id),
       prerender_id(prerender_id),
       url(url),
+      rel_types(rel_types),
       referrer(referrer),
       size(size),
       render_view_route_id(render_view_route_id),
       creation_time(creation_time),
       deferred_launcher(deferred_launcher),
       handle(NULL),
       is_match_complete_replacement(false),
       has_been_abandoned(false) {
 }
 
@@ skipping 90 matching lines @@
       // an abandoned prerender to make room?
       if (!abandoned_prerenders.empty()) {
         CancelPrerender(abandoned_prerenders.front());
         --total_started_prerender_count;
         abandoned_prerenders.pop_front();
       } else {
         return;
       }
     }
 
+    if (!ShouldStartPrerender((*i)->rel_types)) {
+      prerenders_.erase(*i);
+      continue;
+    }
+
     PrerenderHandle* handle = manager_->AddPrerenderFromLinkRelPrerender(
         (*i)->launcher_child_id, (*i)->render_view_route_id,
         (*i)->url, (*i)->referrer, (*i)->size);
     if (!handle) {
       // This prerender couldn't be launched, it's gone.
       prerenders_.erase(*i);
       continue;
     }
 
     // We have successfully started a new prerender.
@@ skipping 137 matching lines @@
   DCHECK(!prerender->is_match_complete_replacement);
   prerender->is_match_complete_replacement = true;
   Send(prerender->launcher_child_id,
        new PrerenderMsg_OnPrerenderStop(prerender->prerender_id));
   // Do not call RemovePrerender here. The replacement needs to stay connected
   // to the HTMLLinkElement in the renderer so it notices renderer-triggered
   // cancelations.
 }
 
 }  // namespace prerender