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

chrome/test/base/ui_test_utils.cc

Index: chrome/test/base/ui_test_utils.cc
diff --git a/chrome/test/base/ui_test_utils.cc b/chrome/test/base/ui_test_utils.cc
index dc6876460af634751ca0e9fd55d8414fefa877c4..a594c1e244540ed91d3e7c1918e0b7a831189838 100644
--- a/chrome/test/base/ui_test_utils.cc
+++ b/chrome/test/base/ui_test_utils.cc
@@ -424,7 +424,7 @@ static void NavigateToURLWithDispositionBlockUntilNavigationsComplete(
       content::NOTIFICATION_TAB_ADDED,
       content::NotificationService::AllSources());
 
-  browser->OpenURL(OpenURLParams(
+  browser->OpenURLFromTab(browser->GetSelectedWebContents(), OpenURLParams(

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

It's unclear how this change is related to the prerender changes.

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

Ah - another great catch. This was related to the NULL web_contents check I had
in MaybeUsePrerenderedPage that is no longer needed. Removed, and un-public'ed
it from browser.

       url, Referrer(), disposition, content::PAGE_TRANSITION_TYPED, false));
   if (browser_test_flags & BROWSER_TEST_WAIT_FOR_BROWSER)
     browser = WaitForBrowserNotInSet(initial_browsers);