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

chrome/test/base/ui_test_utils.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/test/base/ui_test_utils.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
 
@@ skipping 406 matching lines @@
   for (std::vector<Browser*>::const_iterator iter = BrowserList::begin();
        iter != BrowserList::end();
        ++iter) {
     initial_browsers.insert(*iter);
   }
 
   WindowedNotificationObserver tab_added_observer(
       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);
   if (browser_test_flags & BROWSER_TEST_WAIT_FOR_TAB)
     tab_added_observer.Wait();
   if (!(browser_test_flags & BROWSER_TEST_WAIT_FOR_NAVIGATION)) {
     // Some other flag caused the wait prior to this.
     return;
   }
   WebContents* web_contents = NULL;
@@ skipping 665 matching lines @@
   return taker.TakeRenderWidgetSnapshot(rwh, page_size, page_size, bitmap);
 }
 
 bool TakeEntirePageSnapshot(RenderViewHost* rvh, SkBitmap* bitmap) {
   DCHECK(bitmap);
   SnapshotTaker taker;
   return taker.TakeEntirePageSnapshot(rvh, bitmap);
 }
 
 }  // namespace ui_test_utils