gtk: Two fixes for the tab leak:...

gtk: Two fixes for the tab leak:
* The tab strip handles the lifetime of the tab widget, so don't try to increase the ref count in order to destroy the widget later.
* Use DeleteSoon when deleting the dragged tab in order to give gtk a chance to clean up its ref counts added during the drag operation.

BUG=12863
TEST=Extensive tab dragging.  No crashes and the Linux UI valgrind bot should stay green.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=21230

[tony, 2009-07-21 22:55:44]

LGTM if you are confident that there's no race here.

http://codereview.chromium.org/159166/diff/1/4
File chrome/browser/gtk/tabs/tab_strip_gtk.cc (right):

http://codereview.chromium.org/159166/diff/1/4#newcode835
Line 835: MessageLoop::current()->DeleteSoon(FROM_HERE, tab);
You're sure that the gtk d&d api will get to run before the tab is deleted?

[James Hawkins, 2009-07-21 23:04:20]

On 2009/07/21 22:55:44, tony wrote:
> LGTM if you are confident that there's no race here.
> 
> http://codereview.chromium.org/159166/diff/1/4
> File chrome/browser/gtk/tabs/tab_strip_gtk.cc (right):
> 
> http://codereview.chromium.org/159166/diff/1/4#newcode835
> Line 835: MessageLoop::current()->DeleteSoon(FROM_HERE, tab);
> You're sure that the gtk d&d api will get to run before the tab is deleted?

Yes, the current call flow is:

(gtk signal) drag-end
TabGtk::OnDragEnd {
 -> TabStripGtk::EndDrag
  -> DraggedTabControllerGtk::EndDrag
   ...
   -> TabStripGtk::DestroyDraggedSourceTab
    -> delete tab;
}
(gtk) release drag references

And after the patch:

(gtk signal) drag-end
TabGtk::OnDragEnd {
 -> TabStripGtk::EndDrag
  -> DraggedTabControllerGtk::EndDrag
   ...
   -> TabStripGtk::DestroyDraggedSourceTab
    -> DeleteSoon(tab);
}
(gtk) release drag references
delete tab;

So basically in the UI thread, gtk gets control immediately after we return from
handling the drag-end signal and then gets back into the message loop.  There's
no way for us to jump in the middle of this flow before the references are
released.