Remove //mojo/tests.

mojo/tests/BUILD.gn

-# Copyright 2015 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.
-
-import("//testing/test.gni")
-import("//mojo/public/mojo.gni")
-
-test("mojo_task_tracker_perftests") {
-  deps = [
-    "//base/test:test_support",
-    "//mojo/edk/base_edk",
-    "//mojo/edk/system",
-    "//mojo/edk/test:run_all_perftests",
-    "//mojo/environment:chromium",
-    "//mojo/message_pump",
-    "//mojo/public/cpp/bindings",
-    "//mojo/public/cpp/bindings:callback",
-    "//mojo/public/cpp/environment",
-    "//mojo/public/cpp/system",
-    "//mojo/public/cpp/test_support",
-    "//mojo/public/cpp/utility",
-    "//mojo/public/interfaces/bindings/tests:test_interfaces",
-    "//base",
-    "//testing/gtest",
-  ]
-
-  sources = [
-    "task_tracker_perftest.cc",
-  ]
-}