Change single-interface mojo bindings to use SequencedTaskRunner.

mojo/public/cpp/bindings/tests/BUILD.gn

 # 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.
 
 source_set("tests") {
   testonly = true
 
   sources = [
     "associated_interface_unittest.cc",
     "bind_task_runner_unittest.cc",
@@ skipping 115 matching lines @@
     "//mojo/edk/test:test_support",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/system",
     "//mojo/public/cpp/test_support:test_utils",
     "//mojo/public/interfaces/bindings/tests:test_interfaces",
     "//testing/gtest",
   ]
 }
 
 source_set("mojo_public_bindings_test_utils") {
+  testonly = true
+
   sources = [
+    "thread_per_task_sequenced_task_runner.cc",
+    "thread_per_task_sequenced_task_runner.h",
     "validation_test_input_parser.cc",
     "validation_test_input_parser.h",
   ]
 
   deps = [
+    "//base",
     "//mojo/public/c/system",
+    "//testing/gtest",
   ]
 }