Allow new zoom bubble to override current one.

chrome/browser/ui/cocoa/location_bar/zoom_decoration.h

 // Copyright (c) 2012 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_UI_COCOA_LOCATION_BAR_ZOOM_DECORATION_H_
 #define CHROME_BROWSER_UI_COCOA_LOCATION_BAR_ZOOM_DECORATION_H_
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/basictypes.h"
@@ skipping 15 matching lines @@
  public:
   explicit ZoomDecoration(LocationBarViewMac* owner);
   ~ZoomDecoration() override;
 
   // Called when this decoration should show or hide itself in its most current
   // state. Returns whether any updates were made.
   bool UpdateIfNecessary(ui_zoom::ZoomController* zoom_controller);
 
   // Shows the zoom bubble for this decoration. If |auto_close| is YES, then
   // the bubble will automatically close after a fixed period of time.
+  // If a bubble is already showing, the |auto_close| timer is reset.
   void ShowBubble(BOOL auto_close);
 
   // Closes the zoom bubble.
   void CloseBubble();
 
  protected:
   // Hides all UI associated with the zoom decoration.
   // Virtual and protected for testing.
   virtual void HideUI();
 
@@ skipping 26 matching lines @@
   // The bubble that this decoration shows. Weak, owns self.
   ZoomBubbleController* bubble_;
 
   // The string to show for a tooltip.
   base::scoped_nsobject<NSString> tooltip_;
 
   DISALLOW_COPY_AND_ASSIGN(ZoomDecoration);
 };
 
 #endif  // CHROME_BROWSER_UI_COCOA_LOCATION_BAR_ZOOM_DECORATION_H_