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

chrome/browser/sync/sync_setup_wizard.h

Index: chrome/browser/sync/sync_setup_wizard.h
===================================================================
--- chrome/browser/sync/sync_setup_wizard.h	(revision 29327)
+++ chrome/browser/sync/sync_setup_wizard.h	(working copy)
@@ -6,6 +6,7 @@
 #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;
@@ -39,6 +40,10 @@
     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();