WebApps: Adds shutdown notification to AppShortcutManager.

This is necessary so observers know when to remove themselves, as they
might otherwise attempt to remove themselves after the ShortcutManager
has been destroyed, resulting in a use after free.

Bug: 860581
Change-Id: I93f0d4020efdc5633462c8066b47a0a98922e373
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1872083Reviewed-by: Alexey Baskakov <loyso@chromium.org>
Commit-Queue: Jay Harris <harrisjay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#708401}

chrome/browser/web_applications/components/app_shortcut_manager.cc

@@ -38,6 +38,11 @@ void AppShortcutManager::SetSubsystems(AppRegistrar* registrar) {
   registrar_ = registrar;
 }
 
+void AppShortcutManager::Shutdown() {
+  for (auto& observer : observers_)
+    observer.OnShortcutManagerDestroyed();
+}
+
 void AppShortcutManager::AddObserver(AppShortcutObserver* observer) {
   observers_.AddObserver(observer);
 }

chrome/browser/web_applications/components/app_shortcut_manager.h

@@ -33,6 +33,7 @@ class AppShortcutManager {
   virtual ~AppShortcutManager();
 
   void SetSubsystems(AppRegistrar* registrar);
+  void Shutdown();
 
   void AddObserver(AppShortcutObserver* observer);
   void RemoveObserver(AppShortcutObserver* observer);

chrome/browser/web_applications/components/app_shortcut_observer.h

@@ -13,6 +13,7 @@ namespace web_app {
 class AppShortcutObserver : public base::CheckedObserver {
  public:
   virtual void OnShortcutsCreated(const AppId& app_id) {}
+  virtual void OnShortcutManagerDestroyed() {}
 };
 
 }  // namespace web_app

chrome/browser/web_applications/web_app_provider.cc

@@ -149,6 +149,7 @@ void WebAppProvider::Shutdown() {
   pending_app_manager_->Shutdown();
   install_manager_->Shutdown();
   manifest_update_manager_->Shutdown();
+  shortcut_manager_->Shutdown();
 }
 
 void WebAppProvider::StartImpl() {