diff -r 000000000000 -r 6474c204b198 toolkit/devtools/server/tests/unit/test_nesting-02.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/devtools/server/tests/unit/test_nesting-02.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,78 @@
+/* -*- Mode: javascript; js-indent-level: 2; -*- */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test that we can nest event loops and then automatically exit nested event
+// loops when requested.
+
+var gClient;
+var gThreadActor;
+
+function run_test() {
+  initTestDebuggerServer();
+  let gDebuggee = addTestGlobal("test-nesting");
+  gClient = new DebuggerClient(DebuggerServer.connectPipe());
+  gClient.connect(function () {
+    attachTestTabAndResume(gClient, "test-nesting", function (aResponse, aTabClient, aThreadClient) {
+      // Reach over the protocol connection and get a reference to the thread actor.
+      gThreadActor = aThreadClient._transport._serverConnection.getActor(aThreadClient._actor);
+
+      test_nesting();
+    });
+  });
+  do_test_pending();
+}
+
+function test_nesting() {
+  const thread = gThreadActor;
+  const { resolve, reject, promise: p } = promise.defer();
+
+  // The following things should happen (in order):
+  // 1. In the new event loop (created by synchronize)
+  // 2. Resolve the promise (shouldn't exit any event loops)
+  // 3. Exit the event loop (should also then exit synchronize's event loop)
+  // 4. Be after the synchronize call
+  let currentStep = 0;
+
+  executeSoon(function () {
+    let eventLoop;
+
+    executeSoon(function () {
+      // Should be at step 2
+      do_check_eq(++currentStep, 2);
+      // Before resolving, should have the synchronize event loop and the one just created.
+      do_check_eq(thread._nestedEventLoops.size, 2);
+
+      executeSoon(function () {
+        // Should be at step 3
+        do_check_eq(++currentStep, 3);
+        // Before exiting the manually created event loop, should have the
+        // synchronize event loop and the manual event loop.
+        do_check_eq(thread._nestedEventLoops.size, 2);
+        // Should have the event loop
+        do_check_true(!!eventLoop);
+        eventLoop.resolve();
+      });
+
+      resolve(true);
+      // Shouldn't exit any event loops because a new one started since the call to synchronize
+      do_check_eq(thread._nestedEventLoops.size, 2);
+    });
+
+    // Should be at step 1
+    do_check_eq(++currentStep, 1);
+    // Should have only the synchronize event loop
+    do_check_eq(thread._nestedEventLoops.size, 1);
+    eventLoop = thread._nestedEventLoops.push();
+    eventLoop.enter();
+  });
+
+  do_check_eq(thread.synchronize(p), true);
+
+  // Should be on the fourth step
+  do_check_eq(++currentStep, 4);
+  // There shouldn't be any nested event loops anymore
+  do_check_eq(thread._nestedEventLoops.size, 0);
+
+  finishClient(gClient);
+}