[Mac] Tear down extension-installed bubble before main window closes.

chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm

Index: chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm
diff --git a/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm b/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm
index d5e22c3fba7ec0c7c31db3f36ef6fbf3d06b7b80..a42aa3d43d2b31af65f3ec01ff7a92a67573e9b1 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_popup_controller.mm
@@ -171,15 +171,7 @@ class DevtoolsNotificationBridge : public NotificationObserver {
 }
 
 - (void)close {
-  [parentWindow_ removeChildWindow:[self window]];
-
-  // No longer have a parent window, so nil out the pointer and deregister for
-  // notifications.
-  NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
-  [center removeObserver:self
-                    name:NSWindowWillCloseNotification
-                  object:parentWindow_];
-  parentWindow_ = nil;
+  [[[self window] parentWindow] removeChildWindow:[self window]];
   [super close];
 }