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

chrome/browser/prerender/prerender_contents.cc

Index: chrome/browser/prerender/prerender_contents.cc
diff --git a/chrome/browser/prerender/prerender_contents.cc b/chrome/browser/prerender/prerender_contents.cc
index c6355229ebc06cfa4a38c2a4832df6aaccfb9e32..d967fc17b21f05aeb0872722f16f83b16bc21801 100644
--- a/chrome/browser/prerender/prerender_contents.cc
+++ b/chrome/browser/prerender/prerender_contents.cc
@@ -21,7 +21,7 @@
 #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"
@@ -240,6 +240,27 @@ PrerenderContents::Factory* PrerenderContents::CreateFactory() {
   return new PrerenderContentsFactoryImpl();
 }
 
+void BroadcastPrerender(const GURL& url, bool is_add) {
+  content::RenderProcessHost::iterator host_it =
+      content::RenderProcessHost::AllHostsIterator();
+  while (!host_it.IsAtEnd()) {
+    content::RenderProcessHost* host = host_it.GetCurrentValue();
+    host_it.Advance();
+    if (!host)
+      continue;
+    // TODO(cbentzel): Need to filter to the current profile only.

[dominich, 2012/02/28 16:21:00]

Should you also filter to the RPH that was the source of the prerender? That
should be the only one that needs to know about it.

[cbentzel, 2012/02/29 18:16:13]

I am limiting to that now, per your comment as well as creis's.

There may be some prerenders we are dropping on the floor here as a result, but
my guess it it's pretty low. However, this may change if we start doing some
other triggers for prerender such as top sites or co-visited domains.

+    IPC::Message* message = NULL;

[dominich, 2012/02/28 16:21:00]

IPC::Message* message = is_add ? new PrerenderMsg_AddPrerenderURL(url) :
                                 new PrerenderMsg_RemovePrerenderURL(url);

[cbentzel, 2012/02/29 18:16:13]

This doesn't work because then the operands of the ternary operator are
different types. I could do a static_cast to IPC::Message, but then it's verbose
and doesn't buy much.

+    if (is_add) {
+      message = new PrerenderMsg_AddPrerenderURL(url);
+    } else {
+      message = new PrerenderMsg_RemovePrerenderURL(url);
+    }
+    // TODO(cbentzel): Make sure that sending a message doesn't
+    // adjust the iterator.
+    host->Send(message);
+  }
+}
+
 void PrerenderContents::StartPrerendering(
     const RenderViewHost* source_render_view_host,
     SessionStorageNamespace* session_storage_namespace) {
@@ -248,6 +269,8 @@ void PrerenderContents::StartPrerendering(
   DCHECK(prerender_contents_.get() == NULL);
 
   prerendering_has_started_ = true;
+  BroadcastPrerender(prerender_url_, true);
+
   WebContents* new_contents = WebContents::Create(
       profile_, NULL, MSG_ROUTING_NONE, NULL, session_storage_namespace);
   prerender_contents_.reset(new TabContentsWrapper(new_contents));
@@ -418,7 +441,7 @@ void PrerenderContents::Observe(int type,
         // 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));
 
@@ -543,6 +566,7 @@ bool PrerenderContents::ShouldSuppressDialogs() {
 }
 
 void PrerenderContents::Destroy(FinalStatus final_status) {
+  BroadcastPrerender(prerender_url_, false);
   if (prerendering_has_been_cancelled_)
     return;