Initialize TestNavigationObserver::last_navigation_type_ in ctor

With |TestNavigationObserver::last_navigation_type_| initialized properly, it's
possible to use TestNavigationObserver::last_navigation_type() to check whether
a navigation is still ongoing.

Change-Id: Ie814270d5e79bebb95e7ebea05c1ed7eb53bf88c
Reviewed-on: https://chromium-review.googlesource.com/c/1340813Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Wojciech Dzierżanowski <wdzierzanowski@opera.com>
Cr-Commit-Position: refs/heads/master@{#609462}

content/public/test/test_navigation_observer.cc

@@ -129,6 +129,7 @@ TestNavigationObserver::TestNavigationObserver(
       target_url_(target_url),
       last_navigation_succeeded_(false),
       last_net_error_code_(net::OK),
+      last_navigation_type_(NAVIGATION_TYPE_UNKNOWN),
       message_loop_runner_(new MessageLoopRunner(quit_mode)),
       web_contents_created_callback_(
           base::Bind(&TestNavigationObserver::OnWebContentsCreated,