Prerendered pages are swapped in at browser::Navigate time.

chrome/browser/prerender/prerender_contents.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_contents.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/process_util.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/history/history_tab_helper.h"
 #include "chrome/browser/history/history_types.h"
 #include "chrome/browser/prerender/prerender_final_status.h"
 #include "chrome/browser/prerender/prerender_manager.h"
 #include "chrome/browser/prerender/prerender_render_view_host_observer.h"
 #include "chrome/browser/prerender/prerender_tracker.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_list.h"
 #include "chrome/browser/ui/tab_contents/tab_contents_wrapper.h"
 #include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/icon_messages.h"
-#include "chrome/common/render_messages.h"
+#include "chrome/common/prerender_messages.h"
 #include "chrome/common/url_constants.h"
 #include "content/browser/in_process_webkit/session_storage_namespace.h"
 #include "content/browser/renderer_host/render_view_host.h"
 #include "content/browser/renderer_host/resource_request_details.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/web_contents.h"
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/browser/web_contents_view.h"
 #include "ui/gfx/rect.h"
@@ skipping 20 matching lines @@
   bool operator()(const GURL& url) const {
     return url.scheme() == url_.scheme() &&
            url.host() == url_.host() &&
            url.port() == url_.port() &&
            url.path() == url_.path() &&
            url.query() == url_.query();
   }
   GURL url_;
 };
 
+// Tells the render process at |child_id| whether |url| is a new prerendered
+// page, or whether |url| is being removed as a prerendered page. Currently
+// this will only inform the render process that created the prerendered page
+// with <link rel="prerender"> tags about it. This means that if a prerender
+// is created from the omnibox or from another page, clicking on the a link
+// for the same URL in another page will not swap in the prerender.

[dominich, 2012/02/29 18:32:01]

This isn't a problem for Omnibox as we cancel the prerender if the user
navigates somewhere other than we predicted already.

[cbentzel, 2012/02/29 19:22:36]

Done.

+void InformRenderProcessAboutPrerender(const GURL& url,

[dominich, 2012/02/29 18:32:01]

Given this is only called from methods in this class and |url| and |child_id|
are always |prerender_url_| and |creator_child_id_|, it would make more sense as
a private method of the class with a single bool parameter.

[cbentzel, 2012/02/29 19:22:36]

I like it here, because it means that if it changes I don't have to modify the
.h

[dominich, 2012/02/29 19:44:35]

Not modifying a header is a poor reason to base API decisions on. This should be
a class method as it uses state managed by the class. If it should change to be
more complex, then either more state will need to be added to the class, and
it's still correct, or it should be moved to a PrerenderBroadcaster class that
will have its own state.

[cbentzel, 2012/02/29 19:50:10]

Huh? It's a pretty stateless function, and does not directly modify any state
related to that class. That to me screams function.

+                                       bool is_add,
+                                       int child_id) {
+  if (child_id < 0)
+    return;
+  content::RenderProcessHost* render_process_host =
+      content::RenderProcessHost::FromID(child_id);
+  if (!render_process_host)
+    return;
+  IPC::Message* message = NULL;
+  if (is_add) {

[dominich, 2012/02/29 18:32:01]

nit: {} not required

[cbentzel, 2012/02/29 19:22:36]

Done.

+    message = new PrerenderMsg_AddPrerenderURL(url);
+  } else {
+    message = new PrerenderMsg_RemovePrerenderURL(url);
+  }
+  render_process_host->Send(message);
+}
+
 }  // end namespace
 
 class PrerenderContentsFactoryImpl : public PrerenderContents::Factory {
  public:
   virtual PrerenderContents* CreatePrerenderContents(
       PrerenderManager* prerender_manager, PrerenderTracker* prerender_tracker,
       Profile* profile, const GURL& url, const content::Referrer& referrer,
       Origin origin, uint8 experiment_id) OVERRIDE {
     return new PrerenderContents(prerender_manager, prerender_tracker, profile,
                                  url, referrer, origin, experiment_id);
@@ skipping 145 matching lines @@
       profile_(profile),
       page_id_(0),
       has_stopped_loading_(false),
       final_status_(FINAL_STATUS_MAX),
       prerendering_has_started_(false),
       match_complete_status_(MATCH_COMPLETE_DEFAULT),
       prerendering_has_been_cancelled_(false),
       child_id_(-1),
       route_id_(-1),
       origin_(origin),
-      experiment_id_(experiment_id) {
+      experiment_id_(experiment_id),
+      creator_child_id_(-1) {
   DCHECK(prerender_manager != NULL);
 }
 
 bool PrerenderContents::Init() {
   return AddAliasURL(prerender_url_);
 }
 
 // static
 PrerenderContents::Factory* PrerenderContents::CreateFactory() {
   return new PrerenderContentsFactoryImpl();
 }
 
 void PrerenderContents::StartPrerendering(
     const RenderViewHost* source_render_view_host,
     SessionStorageNamespace* session_storage_namespace) {
   DCHECK(profile_ != NULL);
   DCHECK(!prerendering_has_started_);
   DCHECK(prerender_contents_.get() == NULL);
 
   prerendering_has_started_ = true;
+  DCHECK(creator_child_id_ == -1);
+  if (source_render_view_host)
+    creator_child_id_ = source_render_view_host->process()->GetID();
+  InformRenderProcessAboutPrerender(prerender_url_, true,
+                                    creator_child_id_);
+
   WebContents* new_contents = WebContents::Create(
       profile_, NULL, MSG_ROUTING_NONE, NULL, session_storage_namespace);
   prerender_contents_.reset(new TabContentsWrapper(new_contents));
   content::WebContentsObserver::Observe(new_contents);
 
   gfx::Rect tab_bounds;
   if (source_render_view_host) {
     DCHECK(source_render_view_host->view() != NULL);
     WebContents* source_wc =
         source_render_view_host->delegate()->GetAsWebContents();
@@ skipping 150 matching lines @@
 
         content::Details<RenderViewHost> new_render_view_host(details);
         OnRenderViewHostCreated(new_render_view_host.ptr());
 
         // When a new RenderView is created for a prerendering TabContents,
         // tell the new RenderView it's being used for prerendering before any
         // navigations occur.  Note that this is always triggered before the
         // first navigation, so there's no need to send the message just after
         // the TabContents is created.
         new_render_view_host->Send(
-            new ChromeViewMsg_SetIsPrerendering(
+            new PrerenderMsg_SetIsPrerendering(
                 new_render_view_host->routing_id(),
                 true));
 
         // Make sure the size of the RenderViewHost has been passed to the new
         // RenderView.  Otherwise, the size may not be sent until the
         // RenderViewReady event makes it from the render process to the UI
         // thread of the browser process.  When the RenderView receives its
         // size, is also sets itself to be visible, which would then break the
         // visibility API.
         new_render_view_host->WasResized();
@@ skipping 104 matching lines @@
 bool PrerenderContents::ShouldSuppressDialogs() {
   // Always suppress JavaScript messages if they're triggered by a page being
   // prerendered.
   // We still want to show the user the message when they navigate to this
   // page, so cancel this prerender.
   Destroy(FINAL_STATUS_JAVASCRIPT_ALERT);
   return true;
 }
 
 void PrerenderContents::Destroy(FinalStatus final_status) {
+  InformRenderProcessAboutPrerender(prerender_url_, false, creator_child_id_);
   if (prerendering_has_been_cancelled_)
     return;
 
   if (child_id_ != -1 && route_id_ != -1) {
     // Cancel the prerender in the PrerenderTracker.  This is needed
     // because destroy may be called directly from the UI thread without calling
     // TryCancel().  This is difficult to completely avoid, since prerendering
     // can be cancelled before a RenderView is created.
     bool is_cancelled = prerender_tracker_->TryCancel(
         child_id_, route_id_, final_status);
@@ skipping 94 matching lines @@
 bool PrerenderContents::IsCrossSiteNavigationPending() const {
   if (!prerender_contents_.get() || !prerender_contents_->web_contents())
     return false;
   const WebContents* web_contents = prerender_contents_->web_contents();
   return (web_contents->GetSiteInstance() !=
           web_contents->GetPendingSiteInstance());
 }
 
 
 }  // namespace prerender