Add HTTPS Previews Pingback Observer to Init List

Bug: 934865
Change-Id: I92ebfc18b621b66aff1ab1d32ccb2bb7f44212c5
Reviewed-on: https://chromium-review.googlesource.com/c/1482945
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Auto-Submit: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634722}

chrome/browser/page_load_metrics/page_load_metrics_initialize.cc

@@ -34,6 +34,7 @@
 #include "chrome/browser/page_load_metrics/observers/omnibox_suggestion_used_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/page_capping_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/prerender_page_load_metrics_observer.h"
+#include "chrome/browser/page_load_metrics/observers/previews_lite_page_redirect_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/previews_page_load_metrics_observer.h"
 #include "chrome/browser/page_load_metrics/observers/previews_ukm_observer.h"
 #include "chrome/browser/page_load_metrics/observers/protocol_page_load_metrics_observer.h"
@@ -116,6 +117,8 @@ void PageLoadMetricsEmbedder::RegisterObservers(
             previews::OfflinePagePreviewsPageLoadMetricsObserver>());
     tracker->AddObserver(
         std::make_unique<PageCappingPageLoadMetricsObserver>());
+    tracker->AddObserver(
+        std::make_unique<PreviewsLitePageRedirectMetricsObserver>());
     tracker->AddObserver(
         std::make_unique<previews::PreviewsPageLoadMetricsObserver>());
     tracker->AddObserver(std::make_unique<previews::PreviewsUKMObserver>());