Fix issue 174250, crash when reloading packaged app.

chrome/browser/extensions/shell_window_registry.cc

 // 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.
 
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/shell_window_registry.h"
 #include "chrome/browser/profiles/profile_dependency_manager.h"
 #include "chrome/browser/profiles/profile_manager.h"
 #include "chrome/browser/ui/extensions/native_app_window.h"
 #include "chrome/browser/ui/extensions/shell_window.h"
@@ skipping 49 matching lines @@
   FOR_EACH_OBSERVER(Observer, observers_, OnShellWindowAdded(shell_window));
 }
 
 void ShellWindowRegistry::ShellWindowIconChanged(ShellWindow* shell_window) {
   shell_windows_.insert(shell_window);
   FOR_EACH_OBSERVER(Observer, observers_,
                     OnShellWindowIconChanged(shell_window));
 }
 
 void ShellWindowRegistry::RemoveShellWindow(ShellWindow* shell_window) {
-  shell_windows_.erase(shell_window);
-  FOR_EACH_OBSERVER(Observer, observers_, OnShellWindowRemoved(shell_window));
+  size_t num_erased = shell_windows_.erase(shell_window);
+  if (num_erased > 0)
+    FOR_EACH_OBSERVER(Observer, observers_, OnShellWindowRemoved(shell_window));
 }
 
 void ShellWindowRegistry::AddObserver(Observer* observer) {
   observers_.AddObserver(observer);
 }
 
 void ShellWindowRegistry::RemoveObserver(Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
@@ skipping 134 matching lines @@
 
 bool ShellWindowRegistry::Factory::ServiceIsCreatedWithProfile() const {
   return true;
 }
 
 bool ShellWindowRegistry::Factory::ServiceIsNULLWhileTesting() const {
   return false;
 }
 
 }  // namespace extensions