Refactor wait_util so it isn't coupled to EarlGrey.

ios/testing/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("//ios/build/config.gni")
 import("//testing/test.gni")
 
+source_set("ios_test_support") {
+  testonly = true
+
+  deps = [
+    "//base/test:test_support",
+  ]
+
+  sources = [
+    "wait_util.h",
+    "wait_util.mm",
+  ]
+}
+
 source_set("ocmock_support") {
   testonly = true
 
   deps = [
     "//base",
   ]
 
   public_deps = [
     "//third_party/google_toolbox_for_mac",
     "//third_party/ocmock",
@@ skipping 10 matching lines @@
     ":ocmock_support",
     "//base/test:run_all_unittests",
     "//base/test:test_support",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/ocmock",
   ]
 
   assert_no_deps = ios_assert_no_deps
 }