The login dialog was being opened with the main browser window as a parent in...

chrome/browser/sync/sync_setup_wizard.h

 // Copyright (c) 2006-2008 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.
 
 #ifndef CHROME_BROWSER_SYNC_SYNC_SETUP_WIZARD_H_
 #define CHROME_BROWSER_SYNC_SYNC_SETUP_WIZARD_H_
 
 #include "base/basictypes.h"
+#include "app/gfx/native_widget_types.h"
 
 #if defined(OS_LINUX)
 typedef struct _GtkWidget GtkWidget;
 typedef struct _GtkWindow GtkWindow;
 #else
 class SyncSetupFlowContainer;
 #endif
 
 class ProfileSyncService;
 
@@ skipping 13 matching lines @@
     FATAL_ERROR,
     // A final state for when setup completes and it is possible it is the
     // user's first time (globally speaking) as the cloud doesn't have any
     // bookmarks.  We show additional info in this case to explain setting up
     // more computers.
     DONE_FIRST_TIME,
     // A catch-all done case for any setup process.
     DONE
   };
 
+  class WizardParentDelegate {

[tim (not reviewing), 2009/10/29 21:58:44]

I know I suggested going this route with the delegate, but..
upon seeing the extra variable in ProfileSyncService.. I just don't like my idea
anymore.  I think it would be preferable to have a SetParent method on this
wizard class.  It would do nothing if it was already open (already had a flow_).
Otherwise, it would just store it, and use it when it needed to open itself. 
Passing in NULL would be fine, and in this case the code that calls
browser->ShowHTMLDialog would stay as before and lookup the browser window. The
PSS would call SetParent from EnableForUser and ShowLoginDialog.

WDYT? (Really sorry for changing my mind.. it took your work here to make me
realize this)

+    gfx::NativeWindow GetWizardParent();

[tim (not reviewing), 2009/10/29 21:58:44]

<stale comment after prev suggestion>
hmm.. you don't have a default implementation, yet you call this function, don't
you get an unresolved external error? or perhaps you didn't include the cc file
with the impl in the CL?  Also, this isn't declared virtual, so I don't see how
the ProfileSyncService::GetWizardParent would ever be invoked.
</stale comment>

+  };
+
   explicit SyncSetupWizard(ProfileSyncService* service);
   ~SyncSetupWizard();
 
   // Advances the wizard to the specified state if possible, or opens a
   // new dialog starting at |advance_state|.  If the wizard has never ran
   // through to completion, it will always attempt to do so.  Otherwise, e.g
   // for a transient auth failure, it will just run as far as is necessary
   // based on |advance_state| (so for auth failure, up to GAIA_SUCCESS).
   void Step(State advance_state);
 
@@ skipping 21 matching lines @@
   bool visible_;
 #else
   SyncSetupFlowContainer* flow_container_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(SyncSetupWizard);
 };
 
 #endif  // CHROME_BROWSER_SYNC_SYNC_SETUP_WIZARD_H_