1 files changed, 46 insertions, 0 deletions
diff --git a/image/ShutdownTracker.h b/image/ShutdownTracker.h
new file mode 100644
index 000000000..9a38735db
--- /dev/null
+++ b/image/ShutdownTracker.h
@@ -0,0 +1,46 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * ShutdownTracker is an imagelib-global service that allows callers to check
+ * whether shutdown has started.
+ */
+
+#ifndef mozilla_image_ShutdownTracker_h
+#define mozilla_image_ShutdownTracker_h
+
+namespace mozilla {
+namespace image {
+
+/**
+ * ShutdownTracker is an imagelib-global service that allows callers to check
+ * whether shutdown has started. It exists to avoid the need for registering
+ * many 'xpcom-will-shutdown' notification observers on short-lived objects,
+ * which would have an unnecessary performance cost.
+ */
+struct ShutdownTracker
+{
+  /**
+   * Initialize static data. Called during imagelib module initialization.
+   */
+  static void Initialize();
+
+  /**
+   * Check whether shutdown has started. Callers can use this to check whether
+   * it's safe to access XPCOM services; if shutdown has started, such calls
+   * must be avoided.
+   *
+   * @return true if shutdown has already started.
+   */
+  static bool ShutdownHasStarted();
+
+private:
+  virtual ~ShutdownTracker() = 0;  // Forbid instantiation.
+};
+
+} // namespace image
+} // namespace mozilla
+
+#endif // mozilla_image_ShutdownTracker_h