GTK: Even more cleanup to access allocation through the accessor.

chrome/browser/ui/gtk/tabs/tab_gtk.cc

Index: chrome/browser/ui/gtk/tabs/tab_gtk.cc
diff --git a/chrome/browser/ui/gtk/tabs/tab_gtk.cc b/chrome/browser/ui/gtk/tabs/tab_gtk.cc
index 7f8f977587f4dca34ce10c5d6fe2dba9adc84ea7..7b0037a2794107bb5eb2cc237d5fd588eb825406 100644
--- a/chrome/browser/ui/gtk/tabs/tab_gtk.cc
+++ b/chrome/browser/ui/gtk/tabs/tab_gtk.cc
@@ -157,12 +157,15 @@ gboolean TabGtk::OnButtonReleaseEvent(GtkWidget* widget,
     }
   }
 
+  GtkAllocation allocation;
+  gtk_widget_get_allocation(widget, &allocation);
+
   // Middle mouse up means close the tab, but only if the mouse is over it
   // (like a button).
   if (event->button == 2 &&
       event->x >= 0 && event->y >= 0 &&
-      event->x < widget->allocation.width &&
-      event->y < widget->allocation.height) {
+      event->x < allocation.width &&
+      event->y < allocation.height) {
     // If the user is currently holding the left mouse button down but hasn't
     // moved the mouse yet, a drag hasn't started yet.  In that case, clean up
     // some state before closing the tab to avoid a crash.  Once the drag has