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.
Review URL: http://codereview.chromium.org/159166

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@21230 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/gtk/tabs/tab_gtk.cc

@@ -113,7 +113,6 @@ TabGtk::TabGtk(TabDelegate* delegate)
       closing_(false),
       dragging_(false) {
   event_box_ = gtk_event_box_new();
-  g_object_ref(event_box_);
   gtk_event_box_set_visible_window(GTK_EVENT_BOX(event_box_), FALSE);
   gtk_drag_source_set(event_box_, GDK_BUTTON1_MASK,
                       NULL, 0, GDK_ACTION_MOVE);
@@ -150,8 +149,6 @@ TabGtk::~TabGtk() {
     // Invoke this so that we hide the highlight.
     ContextMenuClosed();
   }
-
-  gtk_widget_destroy(event_box_);
 }
 
 // static

chrome/browser/gtk/tabs/tab_strip_gtk.cc

@@ -829,7 +829,10 @@ void TabStripGtk::DestroyDraggedSourceTab(TabGtk* tab) {
   }
 
   gtk_container_remove(GTK_CONTAINER(tabstrip_.get()), tab->widget());
-  delete tab;
+  // If we delete the dragged source tab here, the gtk drag-n-drop API won't
+  // get a change to clean up and remove any references it's added to the tab
+  // widget, so we'll leak the widget.
+  MessageLoop::current()->DeleteSoon(FROM_HERE, tab);
 
   // Force a layout here, because if we've just quickly drag detached a Tab,
   // the stopping of the active animation above may have left the TabStrip in a

tools/valgrind/memcheck/suppressions.txt

@@ -621,18 +621,6 @@
    fun:_ZN7WebCore11ImageSource18createFrameAtIndexEj
    fun:_ZNK11webkit_glue12ImageDecoder6DecodeEPKhj
 }
-{
-   # very common in ui tests
-   bug_12863
-   Memcheck:Leak
-   fun:malloc
-   fun:g_malloc
-   ...
-   fun:gtk_event_box_new
-   fun:_ZN6TabGtkC1EPNS_11TabDelegateE
-   fun:_ZN11TabStripGtk13TabInsertedAtEP11TabContentsib
-   fun:_ZN13TabStripModel19InsertTabContentsAtEiP11TabContentsbb
-}
 {
    bug_15762
    Memcheck:Cond