[ios] Adds test hooks to enable/disable functionality while testing.

ios/chrome/app/tests_fake_hook.mm

Index: ios/chrome/app/tests_fake_hook.mm
diff --git a/ios/chrome/app/tests_fake_hook.mm b/ios/chrome/app/tests_fake_hook.mm
new file mode 100644
index 0000000000000000000000000000000000000000..e4031757e6bb62564029e424a42e3431e44c1a93
--- /dev/null
+++ b/ios/chrome/app/tests_fake_hook.mm
@@ -0,0 +1,24 @@
+// Copyright 2016 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/chrome/app/tests_hook.h"
+
+namespace tests_hook {
+
+bool DisableContextualSearch() {
+  return false;
+}
+bool DisableFirstRun() {
+  return false;
+}
+bool DisableSigninRecallPromo() {
+  return false;
+}
+bool DisableUpdateService() {
+  return false;
+}
+void SetUpTestsIfPresent() {}
+void RunTestsIfPresent() {}
+
+}  // namespace tests_hook