diff -r 000000000000 -r 6474c204b198 toolkit/devtools/server/tests/unit/test_profiler_activation.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/devtools/server/tests/unit/test_profiler_activation.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,66 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const Profiler = Cc["@mozilla.org/tools/profiler;1"].getService(Ci.nsIProfiler);
+
+function connectClient(callback) {
+  let client = new DebuggerClient(DebuggerServer.connectPipe());
+  client.connect(function () {
+    client.listTabs(function(response) {
+      callback(client, response.profilerActor);
+    });
+  });
+}
+
+function run_test()
+{
+  // Ensure the profiler is not running when the test starts (it could
+  // happen if the MOZ_PROFILER_STARTUP environment variable is set)
+  Profiler.StopProfiler();
+
+  DebuggerServer.init(function () { return true; });
+  DebuggerServer.addBrowserActors();
+
+  connectClient((client1, actor1) => {
+    connectClient((client2, actor2) => {
+      activate_first(client1, actor1, client2, actor2);
+    });
+  })
+
+  do_test_pending();
+}
+
+function activate_first(client1, actor1, client2, actor2) {
+  // Start the profiler on the first connection....
+  client1.request({ to: actor1, type: "startProfiler", features: ['js']}, startResponse => {
+    // Profiler should be active now.
+    do_check_true(Profiler.IsActive());
+
+    // But on the next connection just make sure the actor has been
+    // instantiated.
+    client2.request({ to: actor2, type: "getFeatures" }, featureResponse => {
+
+      let connectionClosed = DebuggerServer._connectionClosed;
+      DebuggerServer._connectionClosed = function(conn) {
+        connectionClosed.call(this, conn);
+
+        // Client1 is the only actor that started the profiler,
+        // it shouldn't be active anymore.
+        do_check_false(Profiler.IsActive());
+
+        DebuggerServer._connectionClosed = function(conn) {
+          connectionClosed.call(this, conn);
+
+          // Now there are no open clients at all, it should *definitely*
+          // be deactivated by now.
+          do_check_false(Profiler.IsActive());
+          do_test_finished();
+        }
+        client2.close();
+      };
+      client1.close();
+    });
+  });
+}