Test actual arguments in WebStateImplTest::ObserverTest.

ios/web/public/test/fakes/test_web_state_observer_util.mm

Index: ios/web/public/test/fakes/test_web_state_observer_util.mm
diff --git a/ios/web/public/test/fakes/test_web_state_observer_util.mm b/ios/web/public/test/fakes/test_web_state_observer_util.mm
new file mode 100644
index 0000000000000000000000000000000000000000..9cf1aad00c240e4e85ec495d54de3f8b7b6d9c01
--- /dev/null
+++ b/ios/web/public/test/fakes/test_web_state_observer_util.mm
@@ -0,0 +1,12 @@
+// Copyright 2017 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/web/public/test/fakes/test_web_state_observer_util.h"
+
+#include "ios/web/public/web_state/navigation_context.h"
+
+namespace web {
+TestDidFinishNavigationInfo::TestDidFinishNavigationInfo() {}

[kkhorimoto, 2017/03/02 20:50:40]

Why are these in the .mm file?  Aren't they both the default implementations
supplied by the compiler?  It looks like TestFormActivityInfo and
TestUpdateFaviconUrlCandidatesInfo also include constructors/destructors in
their struct devinitions; why is TestDidFinishNavigationInfo treated
differently?

[Eugene But (OOO till 7-30), 2017/03/02 23:08:48]

TestDidFinishNavigationInfo has a member with non-trivial default constructor.
Without this code compiler is not happy:

../../ios/web/public/test/fakes/test_web_state_observer_util.h:26:1: error:
[chromium-style] Complex class/struct needs an explicit out-of-line constructor.

+TestDidFinishNavigationInfo::~TestDidFinishNavigationInfo() = default;
+}  // namespace web