Add perf tests for async waits using base::MessageLoop.

mojo/environment/BUILD.gn

Index: mojo/environment/BUILD.gn
diff --git a/mojo/environment/BUILD.gn b/mojo/environment/BUILD.gn
index dc21a24da5b428948d368d7d2aacc9c0c18fa1f9..75fd77efdad5936fe717159f58ce1132b05c6900 100644
--- a/mojo/environment/BUILD.gn
+++ b/mojo/environment/BUILD.gn
@@ -2,6 +2,9 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//mojo/public/mojo_application.gni")
+import("//testing/test.gni")
+
 source_set("chromium") {
   sources = [
     "default_async_waiter.cc",
@@ -30,3 +33,24 @@ source_set("chromium") {
     "//mojo/public/cpp/system",
   ]
 }
+
+# TODO(vtl): Just build this as an executable/non-apptest for now. (This
+# requires depending //mojo/edk/test:run_all_perftests, which is undesirable.
+# However, we don't have a good way to automatically run perf tests that are
+# apptests and extract results.)
+test("mojo_environment_perftests") {
+  sources = [
+    "async_wait_perftest.cc",
+  ]
+
+  deps = [
+    ":chromium",
+    "//base",
+    "//base/test:test_support",
+    "//mojo/edk/test:run_all_perftests",
+    "//mojo/message_pump",
+    "//mojo/public/c/environment/tests:perftest_helpers",
+    "//mojo/public/cpp/environment",
+    "//testing/gtest",
+  ]
+}