Chrome should shut down cleanly when quit from the Dock icon menu, during...

chrome/browser/chrome_application_mac.mm

+// 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.
+
+#import "chrome/browser/chrome_application_mac.h"
+
+@implementation CrApplication
+
+// -terminate: is the entry point for orderly "quit" operations in Cocoa.
+// This includes the application menu's quit menu item and keyboard
+// equivalent, the application's dock icon menu's quit menu item, "quit" (not
+// "force quit") in the Activity Monitor, and quits triggered by user logout
+// and system restart and shutdown.
+//
+// The default NSApplication -terminate: implementation will end the process
+// by calling exit(), and thus never leave the main run loop.  This is
+// unsuitable for Chrome's purposes.  Chrome depends on leaving the main
+// run loop to perform a proper orderly shutdown.  This design is ingrained
+// in the application and the assumptions that its code makes, and is
+// entirely reasonable and works well on other platforms, but it's not
+// compatible with the standard Cocoa quit sequence.  Quits originated from
+// within the application can be redirected to not use -terminate:, but
+// quits from elsewhere cannot be.
+//
+// To allow the Cocoa-based Chrome to support the standard Cocoa -terminate:
+// interface, and allow all quits to cause Chrome to shut down properly
+// regardless of their origin, -terminate: is overriden.  The custom
+// -terminate: does not end the application with exit().  Instead, it simply
+// returns after posting the normal NSApplicationWillTerminateNotification
+// notification.  The application is responsible for exiting on its own in
+// whatever way it deems appropriate.  In Chrome's case, the main run loop will
+// end and the applicaton will exit by returning from main().
+//
+// This implementation of -terminate: is scaled back and is not as
+// fully-featured as the implementation in NSApplication, nor is it a direct
+// drop-in replacement -terminate: in most applications.  It is
+// purpose-specific to Chrome.
+- (void)terminate:(id)sender {
+  NSApplicationTerminateReply shouldTerminate = NSTerminateNow;
+  SEL selector = @selector(applicationShouldTerminate:);
+  if ([[self delegate] respondsToSelector:selector])
+    shouldTerminate = [[self delegate] applicationShouldTerminate:self];
+
+  // If shouldTerminate is NSTerminateLater, the application is expected to
+  // call -replyToApplicationShouldTerminate: when it knows whether or not it
+  // should terminate.  If the argument is YES,
+  // -replyToApplicationShouldTerminate: will call -terminate:.  This will
+  // result in another call to the delegate's -applicationShouldTerminate:,
+  // which would be expected to return NSTerminateNow at that point.
+  if (shouldTerminate != NSTerminateNow)
+    return;
+
+  [[NSNotificationCenter defaultCenter]
+      postNotificationName:NSApplicationWillTerminateNotification
+                    object:self];
+
+  // Return, don't exit.  The application is responsible for exiting on its
+  // own.
+}
+
+@end