[Mac] Keep download buttons alive while processing events.

chrome/browser/ui/cocoa/draggable_button.mm

 // Copyright (c) 2011 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.
 
 #import "chrome/browser/ui/cocoa/draggable_button.h"
 
 #include "base/logging.h"
 
 @implementation DraggableButton
 
@@ skipping 18 matching lines @@
 }
 
 - (void)mouseUp:(NSEvent*)theEvent {
   if ([draggableButtonImpl_ mouseUpImpl:theEvent] ==
           kDraggableButtonMixinCallSuper) {
     [super mouseUp:theEvent];
   }
 }
 
 - (void)mouseDown:(NSEvent*)theEvent {
+  // The impl spins an event loop to distinguish clicks from drags,
+  // which could result in our destruction.  Wire ourselves down for
+  // the duration.
+  scoped_nsobject<DraggableButton> keepAlive([self retain]);

[Robert Sesek, 2011/08/23 22:56:48]

Would it be better to do this in the impl?

[Scott Hess - ex-Googler, 2011/08/23 23:04:37]

How?

[Robert Sesek, 2011/08/23 23:10:13]

Retain button_ in the Impl in the loop?

+
   if ([draggableButtonImpl_ mouseDownImpl:theEvent] ==
           kDraggableButtonMixinCallSuper) {
     [super mouseDown:theEvent];
   }
 }
 
 - (void)beginDrag:(NSEvent*)dragEvent {
   // Must be overridden by subclasses.
   NOTREACHED();
 }
 
 @end  // @interface DraggableButton