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

chrome/browser/views/constrained_window_win.cc

Index: chrome/browser/views/constrained_window_win.cc
diff --git a/chrome/browser/views/constrained_window_win.cc b/chrome/browser/views/constrained_window_win.cc
index c94576e4e1667f27c3a75d9ee5078c95198fffa9..10d4bbb3a70bcb2972824fbd5709dd06a5baab7f 100644
--- a/chrome/browser/views/constrained_window_win.cc
+++ b/chrome/browser/views/constrained_window_win.cc
@@ -592,6 +592,10 @@ views::NonClientFrameView* ConstrainedWindowWin::CreateFrameViewForWindow() {
   return new ConstrainedWindowFrameView(this);
 }
 
+void ConstrainedWindowWin::ShowConstrainedWindow() {
+  ActivateConstrainedWindow();
+}
+
 void ConstrainedWindowWin::CloseConstrainedWindow() {
   // Broadcast to all observers of NOTIFY_CWINDOW_CLOSED.
   // One example of such an observer is AutomationCWindowTracker in the
@@ -632,7 +636,6 @@ ConstrainedWindowWin::ConstrainedWindowWin(
   set_focus_on_creation(false);
 
   WindowWin::Init(owner_->GetNativeView(), gfx::Rect());
-  ActivateConstrainedWindow();
 }
 
 void ConstrainedWindowWin::ActivateConstrainedWindow() {