Add <link rel=next> support to prerender.

chrome/browser/prerender/prerender_link_manager.cc

Index: chrome/browser/prerender/prerender_link_manager.cc
diff --git a/chrome/browser/prerender/prerender_link_manager.cc b/chrome/browser/prerender/prerender_link_manager.cc
index 7726016c203f430ee05bb727dc56b28e7e8a7a64..fa76f5596a2f0aca59ea24f163b61609d94143fb 100644
--- a/chrome/browser/prerender/prerender_link_manager.cc
+++ b/chrome/browser/prerender/prerender_link_manager.cc
@@ -6,15 +6,18 @@
 
 #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"
@@ -29,6 +32,12 @@ using content::SessionStorageNamespace;
 
 namespace {
 
+bool ShouldStartRelNextPrerenders() {
+  const std::string experiment_name =
+      base::FieldTrialList::FindFullName("PrerenderRelNextTrial");
+  return experiment_name.find("Yes") != std::string::npos;
+}
+
 void Send(int child_id, IPC::Message* raw_message) {
   using content::RenderProcessHost;
   scoped_ptr<IPC::Message> own_message(raw_message);
@@ -44,7 +53,8 @@ void Send(int child_id, IPC::Message* raw_message) {
 namespace prerender {
 
 PrerenderLinkManager::PrerenderLinkManager(PrerenderManager* manager)
-    : has_shutdown_(false),
+    : should_start_rel_next_prerenders_(ShouldStartRelNextPrerenders()),
+      has_shutdown_(false),
       manager_(manager) {
 }
 
@@ -64,6 +74,7 @@ PrerenderLinkManager::~PrerenderLinkManager() {
 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) {
@@ -78,7 +89,7 @@ void PrerenderLinkManager::OnAddPrerender(int launcher_child_id,
     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());
   prerenders_.push_back(prerender);
   StartPrerenders();
@@ -135,12 +146,14 @@ 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) : 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),
@@ -247,6 +260,22 @@ void PrerenderLinkManager::StartPrerenders() {
       }
     }
 
+    switch ((*i)->rel_types) {
+      case PrerenderRelTypePrerender:
+      case PrerenderRelTypePrerender | PrerenderRelTypeNext:
+        break;
+
+      case PrerenderRelTypeNext:
+        if (should_start_rel_next_prerenders_)
+          break;
+        else
+          continue;
+
+      case 0:
+      default:
+        NOTREACHED();
+    }
+

[davidben, 2013/12/19 20:30:03]

Nit: Maybe split this off into a separate function and check each bit
individually? Something like

if (!ShouldLaunchPrerender(*i))
  continue;

bool PrerenderLinkManager::ShouldLaunchPrerender(LinkPrerender* prerender) {
  DCHECK_NE(0, prerender->rel_types);
  if (prerender->rel_types & PrerenderRelTypePrerender)
    return true;
  if (should_start_rel_next_prerenders_ &&
      (prerender->rel_types & PrerenderRelTypeNext))
    return true;
  return false;
}

The switch-case on a bitmask looks a little goofy. :-) Also this way adding a
new field doesn't have to be multisided.

[gavinp, 2013/12/20 14:44:48]

Done.

     PrerenderHandle* handle = manager_->AddPrerenderFromLinkRelPrerender(
         (*i)->launcher_child_id, (*i)->render_view_route_id,
         (*i)->url, (*i)->referrer, (*i)->size);