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

chrome/browser/cocoa/constrained_window_mac.h

 // Copyright (c) 2009 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_COCOA_CONSTRAINED_WINDOW_MAC_H_
 #define CHROME_BROWSER_COCOA_CONSTRAINED_WINDOW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "chrome/browser/tab_contents/constrained_window.h"
@@ skipping 99 matching lines @@
 // Constrained windows work slightly differently on OS X than on the other
 // platforms:
 // 1. A constrained window is bound to both a tab and window on OS X.
 // 2. The delegate is responsible for closing the sheet again when it is
 //    deleted.
 class ConstrainedWindowMac : public ConstrainedWindow {
  public:
   virtual ~ConstrainedWindowMac();
 
   // Overridden from ConstrainedWindow:
+  virtual void ShowConstrainedWindow();
   virtual void CloseConstrainedWindow();
 
   // Returns the TabContents that constrains this Constrained Window.
   TabContents* owner() const { return owner_; }
 
   // Returns the window's delegate.
   ConstrainedWindowMacDelegate* delegate() { return delegate_; }
 
   // Makes the constrained window visible, if it is not yet visible.
   void Realize(BrowserWindowController* controller);
 
  private:
   friend class ConstrainedWindow;
 
   ConstrainedWindowMac(TabContents* owner,
                        ConstrainedWindowMacDelegate* delegate);
 
   // The TabContents that owns and constrains this ConstrainedWindow.
   TabContents* owner_;
 
   // Delegate that provides the contents of this constrained window.
   ConstrainedWindowMacDelegate* delegate_;
 
   // Controller of the window that contains this sheet.
   BrowserWindowController* controller_;
 
+  // Stores if |ShowConstrainedWindow()| was called.
+  bool should_be_visible_;
+
   DISALLOW_COPY_AND_ASSIGN(ConstrainedWindowMac);
 };
 
 #endif  // CHROME_BROWSER_COCOA_CONSTRAINED_WINDOW_MAC_H_