Similar as extension, DOM UI needs to be created in its own process....

chrome/browser/tab_contents/render_view_host_manager_unittest.cc

 // Copyright (c) 2010 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/browser_thread.h"
 #include "chrome/browser/browser_url_handler.h"
 #include "chrome/browser/renderer_host/site_instance.h"
 #include "chrome/browser/renderer_host/test/test_render_view_host.h"
 #include "chrome/browser/tab_contents/navigation_controller.h"
 #include "chrome/browser/tab_contents/navigation_entry.h"
@@ skipping 235 matching lines @@
 
   GURL url(chrome::kChromeUINewTabURL);
   NavigationEntry entry(NULL /* instance */, -1 /* page_id */, url,
                         GURL() /* referrer */, string16() /* title */,
                         PageTransition::TYPED);
   RenderViewHost* host = manager.Navigate(entry);
 
   EXPECT_TRUE(host);
   EXPECT_TRUE(host == manager.current_host());
   EXPECT_FALSE(manager.pending_render_view_host());
-  EXPECT_TRUE(manager.pending_dom_ui());
-  EXPECT_FALSE(manager.dom_ui());
 
   // It's important that the site instance get set on the DOM UI page as soon
   // as the navigation starts, rather than lazily after it commits, so we don't
   // try to re-use the SiteInstance/process for non DOM-UI things that may
   // get loaded in between.
   EXPECT_TRUE(host->site_instance()->has_site());
   EXPECT_EQ(url, host->site_instance()->site());
 
-  // Commit.
-  manager.DidNavigateMainFrame(host);

[Charlie Reis, 2011/01/07 23:40:37]

Let's keep this commit block as the last line of the test (below the DOMUI
related EXPECTs), just to prevent regressions in DidNavigateMainFrame in this
case.

-
   EXPECT_FALSE(manager.pending_dom_ui());

[Charlie Reis, 2011/01/07 23:40:37]

Let's put a comment above this line saying that the DOMUI is committed
immediately because the RenderViewHost has not been used yet.  It'll help others
understand why the change was needed.

   EXPECT_TRUE(manager.dom_ui());
 }
 
 // Tests that chrome: URLs that are not DOM UI pages do not get grouped into
 // DOM UI renderers, even if --process-per-tab is enabled.  In that mode, we
 // still swap processes if ShouldSwapProcessesForNavigation is true.
 // Regression test for bug 46290.
 TEST_F(RenderViewHostManagerTest, NonDOMUIChromeURLs) {
   SiteInstance* instance = SiteInstance::CreateSiteInstance(profile_.get());
   TestTabContents tab_contents(profile_.get(), instance);
@@ skipping 59 matching lines @@
   // That should have cancelled the pending RVH, and the evil RVH should be the
   // current one.
   EXPECT_TRUE(contents()->render_manager()->pending_render_view_host() == NULL);
   EXPECT_EQ(evil_rvh, contents()->render_manager()->current_host());
 
   // Also we should not have a pending navigation entry.
   NavigationEntry* entry = contents()->controller().GetActiveEntry();
   ASSERT_TRUE(entry != NULL);
   EXPECT_EQ(url2, entry->url());
 }