diff -r 000000000000 -r 6474c204b198 security/manager/ssl/src/CryptoTask.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/security/manager/ssl/src/CryptoTask.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,93 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef mozilla__CryptoTask_h
+#define mozilla__CryptoTask_h
+
+#include "mozilla/Attributes.h"
+#include "nsThreadUtils.h"
+#include "nsNSSShutDown.h"
+
+namespace mozilla {
+
+/**
+ * Frequently we need to run a task on a background thread without blocking
+ * the main thread, and then call a callback on the main thread with the
+ * result. This class provides the framework for that. Subclasses must:
+ *
+ *   (1) Override CalculateResult for the off-the-main-thread computation.
+ *       NSS functionality may only be accessed within CalculateResult.
+ *   (2) Override ReleaseNSSResources to release references to all NSS
+ *       resources (that do implement nsNSSShutDownObject themselves).
+ *   (3) Override CallCallback() for the on-the-main-thread call of the
+ *       callback.
+ *
+ * CalculateResult, ReleaseNSSResources, and CallCallback are called in order,
+ * except CalculateResult might be skipped if NSS is shut down before it can
+ * be called; in that case ReleaseNSSResources will be called and then
+ * CallCallback will be called with an error code.
+ */
+class CryptoTask : public nsRunnable,
+                   public nsNSSShutDownObject
+{
+public:
+  template <size_t LEN>
+  nsresult Dispatch(const char (&taskThreadName)[LEN])
+  {
+    static_assert(LEN <= 15,
+                  "Thread name must be no more than 15 characters");
+    // Can't add 'this' as the event to run, since mThread may not be set yet
+    nsresult rv = NS_NewNamedThread(taskThreadName, getter_AddRefs(mThread));
+    if (NS_SUCCEEDED(rv)) {
+      // Note: event must not null out mThread!
+      rv = mThread->Dispatch(this, NS_DISPATCH_NORMAL);
+    }
+    return rv;
+  }
+
+protected:
+  CryptoTask()
+    : mRv(NS_ERROR_NOT_INITIALIZED),
+      mReleasedNSSResources(false)
+  {
+  }
+
+  virtual ~CryptoTask();
+
+  /**
+   * Called on a background thread (never the main thread). If CalculateResult
+   * is called, then its result will be passed to CallCallback on the main
+   * thread.
+   */
+  virtual nsresult CalculateResult() = 0;
+
+  /**
+   * Called on the main thread during NSS shutdown or just before CallCallback
+   * has been called. All NSS resources must be released. Usually, this just
+   * means assigning nullptr to the ScopedNSSType-based memory variables.
+   */
+  virtual void ReleaseNSSResources() = 0;
+
+  /**
+   * Called on the main thread with the result from CalculateResult() or
+   * with an error code if NSS was shut down before CalculateResult could
+   * be called.
+   */
+  virtual void CallCallback(nsresult rv) = 0;
+
+private:
+  NS_IMETHOD Run() MOZ_OVERRIDE MOZ_FINAL;
+  virtual void virtualDestroyNSSReference() MOZ_OVERRIDE MOZ_FINAL;
+
+  nsresult mRv;
+  bool mReleasedNSSResources;
+
+  nsCOMPtr<nsIThread> mThread;
+};
+
+} // namespace mozilla
+
+#endif // mozilla__CryptoTask_h