Change single-interface mojo bindings to use SequencedTaskRunner.

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

Index: mojo/public/cpp/bindings/tests/BUILD.gn
diff --git a/mojo/public/cpp/bindings/tests/BUILD.gn b/mojo/public/cpp/bindings/tests/BUILD.gn
index 71305b8efc7c7e21c3e91e31432e0a1cd933c4ef..20a29dfa775bffeef76da6c6e95ca067fa3a9426 100644
--- a/mojo/public/cpp/bindings/tests/BUILD.gn
+++ b/mojo/public/cpp/bindings/tests/BUILD.gn
@@ -133,12 +133,18 @@ source_set("perftests") {
 }
 
 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",
   ]
 }