Add support for writing unit tests for Mojo-backed apps/extensions APIs.

extensions/renderer/resources/browser_test_environment_specific_bindings.js

Index: extensions/renderer/resources/browser_test_environment_specific_bindings.js
diff --git a/extensions/renderer/resources/browser_test_environment_specific_bindings.js b/extensions/renderer/resources/browser_test_environment_specific_bindings.js
new file mode 100644
index 0000000000000000000000000000000000000000..f5408628db175b7d442f33307f75d3432419bbcb
--- /dev/null
+++ b/extensions/renderer/resources/browser_test_environment_specific_bindings.js
@@ -0,0 +1,15 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+function registerHooks(api) {
+}
+
+function testDone(runNextTest) {
+  // Use setTimeout here to allow previous test contexts to be
+  // eligible for garbage collection.
+  setTimeout(runNextTest, 0);
+}
+
+exports.registerHooks = registerHooks;
+exports.testDone = testDone;