Fix ios_chrome_unittests to crash on DCHECK failure.

ios/chrome/browser/ui/settings/personal_data_manager_data_changed_observer.cc

Index: ios/chrome/browser/ui/settings/personal_data_manager_data_changed_observer.cc
diff --git a/ios/chrome/browser/ui/settings/personal_data_manager_data_changed_observer.cc b/ios/chrome/browser/ui/settings/personal_data_manager_data_changed_observer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..a7e55387d1a28c4eabb483a3b9ca982473b029ae
--- /dev/null
+++ b/ios/chrome/browser/ui/settings/personal_data_manager_data_changed_observer.cc
@@ -0,0 +1,26 @@
+// 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.
+
+#include "ios/chrome/browser/ui/settings/personal_data_manager_data_changed_observer.h"
+
+#include "components/autofill/core/browser/personal_data_manager.h"
+
+PersonalDataManagerDataChangedObserver::PersonalDataManagerDataChangedObserver(
+    autofill::PersonalDataManager* personal_data_manager)
+    : personal_data_manager_(personal_data_manager) {
+  personal_data_manager_->AddObserver(this);
+}
+
+PersonalDataManagerDataChangedObserver::
+    ~PersonalDataManagerDataChangedObserver() {
+  personal_data_manager_->RemoveObserver(this);
+}
+
+void PersonalDataManagerDataChangedObserver::Wait() {
+  run_loop_.Run();
+}
+
+void PersonalDataManagerDataChangedObserver::OnPersonalDataChanged() {
+  run_loop_.QuitWhenIdle();

[noyau (Ping after 24h), 2016/12/22 13:17:22]

Any risks of this not being called at all?

[sdefresne, 2016/12/22 13:28:12]

If this is not called, it means that no method causing a modification of the
PersonalDataManager was called since the creation of this object. This would
indicate a bug in the test (either it should not wait for a modification or it
should create the object before asking for the modification).

+}