diff -r 000000000000 -r 6474c204b198 netwerk/ipc/ChannelEventQueue.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/netwerk/ipc/ChannelEventQueue.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,181 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set sw=2 ts=8 et 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_net_ChannelEventQueue_h
+#define mozilla_net_ChannelEventQueue_h
+
+#include <nsTArray.h>
+#include <nsAutoPtr.h>
+
+class nsISupports;
+class nsIEventTarget;
+class nsIThread;
+
+namespace mozilla {
+namespace net {
+
+class ChannelEvent
+{
+ public:
+  ChannelEvent() { MOZ_COUNT_CTOR(ChannelEvent); }
+  virtual ~ChannelEvent() { MOZ_COUNT_DTOR(ChannelEvent); }
+  virtual void Run() = 0;
+};
+
+// Workaround for Necko re-entrancy dangers. We buffer IPDL messages in a
+// queue if still dispatching previous one(s) to listeners/observers.
+// Otherwise synchronous XMLHttpRequests and/or other code that spins the
+// event loop (ex: IPDL rpc) could cause listener->OnDataAvailable (for
+// instance) to be dispatched and called before mListener->OnStartRequest has
+// completed.
+
+class AutoEventEnqueuerBase;
+
+class ChannelEventQueue MOZ_FINAL
+{
+  NS_INLINE_DECL_REFCOUNTING(ChannelEventQueue)
+
+ public:
+  ChannelEventQueue(nsISupports *owner)
+    : mSuspendCount(0)
+    , mSuspended(false)
+    , mForced(false)
+    , mFlushing(false)
+    , mOwner(owner) {}
+
+  // Checks to determine if an IPDL-generated channel event can be processed
+  // immediately, or needs to be queued using Enqueue().
+  inline bool ShouldEnqueue();
+
+  // Puts IPDL-generated channel event into queue, to be run later
+  // automatically when EndForcedQueueing and/or Resume is called.
+  inline void Enqueue(ChannelEvent* callback);
+
+  // After StartForcedQueueing is called, ShouldEnqueue() will return true and
+  // no events will be run/flushed until EndForcedQueueing is called.
+  // - Note: queueing may still be required after EndForcedQueueing() (if the
+  //   queue is suspended, etc):  always call ShouldEnqueue() to determine
+  //   whether queueing is needed.
+  inline void StartForcedQueueing();
+  inline void EndForcedQueueing();
+
+  // Suspend/resume event queue.  ShouldEnqueue() will return true and no events
+  // will be run/flushed until resume is called.  These should be called when
+  // the channel owning the event queue is suspended/resumed.
+  inline void Suspend();
+  // Resume flushes the queue asynchronously, i.e. items in queue will be
+  // dispatched in a new event on the current thread.
+  void Resume();
+
+  // Retargets delivery of events to the target thread specified.
+  nsresult RetargetDeliveryTo(nsIEventTarget* aTargetThread);
+
+ private:
+  // Private destructor, to discourage deletion outside of Release():
+  ~ChannelEventQueue()
+  {
+  }
+
+  inline void MaybeFlushQueue();
+  void FlushQueue();
+  inline void CompleteResume();
+
+  nsTArray<nsAutoPtr<ChannelEvent> > mEventQueue;
+
+  uint32_t mSuspendCount;
+  bool     mSuspended;
+  bool mForced;
+  bool mFlushing;
+
+  // Keep ptr to avoid refcount cycle: only grab ref during flushing.
+  nsISupports *mOwner;
+
+  // Target thread for delivery of events.
+  nsCOMPtr<nsIThread> mTargetThread;
+
+  friend class AutoEventEnqueuer;
+};
+
+inline bool
+ChannelEventQueue::ShouldEnqueue()
+{
+  bool answer =  mForced || mSuspended || mFlushing;
+
+  NS_ABORT_IF_FALSE(answer == true || mEventQueue.IsEmpty(),
+                    "Should always enqueue if ChannelEventQueue not empty");
+
+  return answer;
+}
+
+inline void
+ChannelEventQueue::Enqueue(ChannelEvent* callback)
+{
+  mEventQueue.AppendElement(callback);
+}
+
+inline void
+ChannelEventQueue::StartForcedQueueing()
+{
+  mForced = true;
+}
+
+inline void
+ChannelEventQueue::EndForcedQueueing()
+{
+  mForced = false;
+  MaybeFlushQueue();
+}
+
+inline void
+ChannelEventQueue::Suspend()
+{
+  mSuspended = true;
+  mSuspendCount++;
+}
+
+inline void
+ChannelEventQueue::CompleteResume()
+{
+  // channel may have been suspended again since Resume fired event to call this.
+  if (!mSuspendCount) {
+    // we need to remain logically suspended (for purposes of queuing incoming
+    // messages) until this point, else new incoming messages could run before
+    // queued ones.
+    mSuspended = false;
+    MaybeFlushQueue();
+  }
+}
+
+inline void
+ChannelEventQueue::MaybeFlushQueue()
+{
+  // Don't flush if forced queuing on, we're already being flushed, or
+  // suspended, or there's nothing to flush
+  if (!mForced && !mFlushing && !mSuspended && !mEventQueue.IsEmpty())
+    FlushQueue();
+}
+
+// Ensures that ShouldEnqueue() will be true during its lifetime (letting
+// caller know incoming IPDL msgs should be queued). Flushes the queue when it
+// goes out of scope.
+class AutoEventEnqueuer
+{
+ public:
+  AutoEventEnqueuer(ChannelEventQueue *queue) : mEventQueue(queue) {
+    mEventQueue->StartForcedQueueing();
+  }
+  ~AutoEventEnqueuer() {
+    mEventQueue->EndForcedQueueing();
+  }
+ private:
+  ChannelEventQueue* mEventQueue;
+};
+
+}
+}
+
+#endif