diff -r 000000000000 -r 6474c204b198 tools/profiler/ProfilerIOInterposeObserver.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/profiler/ProfilerIOInterposeObserver.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,30 @@
+/* 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/. */
+
+#include "GeckoProfiler.h"
+#include "ProfilerIOInterposeObserver.h"
+#include "ProfilerMarkers.h"
+
+using namespace mozilla;
+
+void ProfilerIOInterposeObserver::Observe(Observation& aObservation)
+{
+  if (!IsMainThread()) {
+    return;
+  }
+
+  ProfilerBacktrace* stack = profiler_get_backtrace();
+
+  nsCString filename;
+  if (aObservation.Filename()) {
+    filename = NS_ConvertUTF16toUTF8(aObservation.Filename());
+  }
+
+  IOMarkerPayload* markerPayload = new IOMarkerPayload(aObservation.Reference(),
+                                                       filename.get(),
+                                                       aObservation.Start(),
+                                                       aObservation.End(),
+                                                       stack);
+  PROFILER_MARKER_PAYLOAD(aObservation.ObservedOperationString(), markerPayload);
+}