Enforce that only one constrained window is displayed at once per tab.

chrome/browser/gtk/constrained_window_gtk.cc

Index: chrome/browser/gtk/constrained_window_gtk.cc
diff --git a/chrome/browser/gtk/constrained_window_gtk.cc b/chrome/browser/gtk/constrained_window_gtk.cc
index 1f53a59efde8a95094a0a98c260f1a1380a19ada..c6380d675e9fd052627ced8365d74393ea077c6b 100644
--- a/chrome/browser/gtk/constrained_window_gtk.cc
+++ b/chrome/browser/gtk/constrained_window_gtk.cc
@@ -11,7 +11,8 @@
 ConstrainedWindowGtk::ConstrainedWindowGtk(
     TabContents* owner, ConstrainedWindowGtkDelegate* delegate)
     : owner_(owner),
-      delegate_(delegate) {
+      delegate_(delegate),
+      visible_(false) {
   DCHECK(owner);
   DCHECK(delegate);
   GtkWidget* dialog = delegate->GetWidgetRoot();
@@ -29,20 +30,25 @@ ConstrainedWindowGtk::ConstrainedWindowGtk(
   gtk_container_add(GTK_CONTAINER(frame), alignment);
   gtk_container_add(GTK_CONTAINER(ebox), frame);
   border_.Own(ebox);
+}
+
+ConstrainedWindowGtk::~ConstrainedWindowGtk() {
+  border_.Destroy();
+}
 
+void ConstrainedWindowGtk::ShowConstrainedWindow() {
   gtk_widget_show_all(border_.get());
 
   // We collaborate with TabContentsViewGtk and stick ourselves in the
   // TabContentsViewGtk's floating container.
   ContainingView()->AttachConstrainedWindow(this);
-}
 
-ConstrainedWindowGtk::~ConstrainedWindowGtk() {
-  border_.Destroy();
+  visible_ = true;
 }
 
 void ConstrainedWindowGtk::CloseConstrainedWindow() {
-  ContainingView()->RemoveConstrainedWindow(this);
+  if (visible_)
+    ContainingView()->RemoveConstrainedWindow(this);
   delegate_->DeleteDelegate();
   owner_->WillClose(this);